Currently, this can be achieve with this code:
  TextInfo textInfo = new CultureInfo("en-US", false).TextInfo;
        bool updating = false;
        void radTextBox1_TextChanging(object sender, TextChangingEventArgs e)
        {
            if (!updating)
            {
                int pos = radTextBox1.TextBoxElement.TextBoxItem.SelectionStart;
                updating = true;
                radTextBox1.Text = textInfo.ToTitleCase(radTextBox1.Text);
                radTextBox1.TextBoxElement.TextBoxItem.SelectionStart = pos;
                updating = false;
            }
        }

Users should be able to increment the whole value of the RadMaskedEditBox using the Up/Down arrow keys or Mouse Wheel

ADD. RadTextBox - there should be a mode whether the undo should bring back the previous word or to work for each character

ADD. RadTextBox - add redo functionality

The textbox should increase its size when entering text.

One should be able to change the color of the RadTextBox text when it is disabled.

Workaround: override the ProcessCmdKey method of the form and activate the desired control:
 protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
        {
            if (keyData== Keys.Tab)
            {
                this.ActiveControl = this.radPopupEditor2.PopupEditorElement.TextBoxElement.TextBoxItem.HostedControl;
                return true;
            }
            return base.ProcessCmdKey(ref msg, keyData);
        }

IMPORTANT!!! Tab key should navigate to the next control even if the popup is opened.

To reproduce:
- Use the following format:
radDateTimePicker1.Format = DateTimePickerFormat.Custom;
radDateTimePicker1.CustomFormat = "MM/dd/yyyy";

- Clear the date and try to enter 01/01/2017 (see attched video) 

Workaround:
 radDateTimePicker1.NullDate = DateTime.MinValue.AddYears(1);

to reproduce this bug :
add RadDateTimePicker and set culture to fa-IR
change the header navigation mode to zoom with : 
Me.radDateTimePicker1.DateTimePickerElement.Calendar.HeaderNavigationMode = HeaderNavigationMode.Zoom
popup the date time picker then georgian dates are displayed
i'll attach screenshots of what happening.

How to reproduce:
Just open the popup with the Alt and Down arrow key combination, you will notice that the value changes

Workaround: 
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.radDateTimePicker1.DateTimePickerElement.KeyDown += DateTimePickerElement_KeyDown;
    }

    private void DateTimePickerElement_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.F4 || (e.KeyData == (Keys.Alt | Keys.Down)))
        {
            e.Handled = true;
        }
    }
}

To reproduce:
public Form1()
{
    InitializeComponent();

    this.radTextBox1.Text = "abcd";
    this.radTextBox2.Text = "abcd";
    this.radTextBoxControl1.Text = "abcd";
    this.radTextBoxControl2.Text = "abcd";

    this.radTextBox2.Multiline = true;
    this.radTextBoxControl2.Multiline = true;

    this.textBox1.Text= "abcd";
    this.textBox2.Text= "abcd";
    this.textBox2.Multiline = true;
}

Workaround: set the Multiline property to true in the Form.Load event.

Second workaround: this.radTextBox2.TextBoxElement.TextBoxItem.Margin = new Padding(-2, 0, 0, 0);

To reproduce:
- select the whole date and press delete.
- the value should be cleared at this point not when the control loses the focus.

Workaround:

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        AddHandler RadDateTimePicker1.KeyDown, AddressOf KeyDown_EventHandler
    End Sub

    Private Sub KeyDown_EventHandler(sender As Object, e As KeyEventArgs)
        If e.KeyData = Keys.Delete Then
            e.Handled = True
            RadDateTimePicker1.SetToNullValue()
        End If
    End Sub

To reproduce: Add a RadTextBoxControl and set the SelectionColor property to Red. You will notice that the selection color is semi-transparent and it seems like pink. In order to obtain real Red selection color, it is necessary to set the SelectionOpacity property to 255. However, the selected text is not visible. Please refer to the attached screenshot.

Workaround:

public class CustomTextBoxControl : RadTextBoxControl
{
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadTextBoxControl).FullName;
        }
    }
    protected override RadTextBoxControlElement CreateTextBoxElement()
    {
        return new CustomRadTextBoxControlElement();
    }
}

public class CustomRadTextBoxControlElement : RadTextBoxControlElement
{
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(RadTextBoxControlElement);
        }
    }
    protected override TextBoxViewElement CreateViewElement()
    {
        return new CustomTextBoxViewElement();
    }
}

public class CustomTextBoxViewElement : TextBoxViewElement
{
    protected override void PaintChildren(IGraphics graphics, Rectangle clipRectange, float angle, 
        SizeF scale, bool useRelativeTransformation)
    {
        this.SelectionPrimitive.PaintPrimitive(graphics, angle, scale);
        base.PaintChildren(graphics, clipRectange, angle, scale, useRelativeTransformation);
    }

    protected override void PostPaintChildren(IGraphics graphics, Rectangle clipRectange, float angle, SizeF scale)
    {
        if (this.SelectionPrimitive == null)
        {
            return;
        }

        if (this.Multiline && this.WordWrap)
        {
            this.SelectionPrimitive.TextBoxElement.Navigator.RestoreSelection();
        }
    }
}

To reproduce: 
1. Enter some text and click the first button. Both properties, Text and Value contain the expected value.
2. Click the second button to clear the text and value.
3. Enter some text again and click the first button. You will notice that the Value remains empty. 

public RadForm1()
{
    InitializeComponent();

    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.None;
    this.radMaskedEditBox1.Mask = "CCCCCCC";
}

private void radButton1_Click(object sender, EventArgs e)
{
    this.radLabel1.Text = "Text: " + this.radMaskedEditBox1.Text;
    this.radLabel2.Text = "Value: " + this.radMaskedEditBox1.Value + "";
}

private void radButton2_Click(object sender, EventArgs e)
{
    this.radMaskedEditBox1.Clear();
}

Workaround: use MaskType.Standard

The issue exist in the versions after Q1 2017

Workaround:
Class MyTextBox
    Inherits RadTextBoxControl

    Protected Overrides Function CreateTextBoxElement() As RadTextBoxControlElement
        Return New MyTextBoxElement()

    End Function
End Class

Class MyTextBoxElement
    Inherits RadTextBoxControlElement
    Protected Overrides ReadOnly Property ThemeEffectiveType As Type
        Get
            Return GetType(RadTextBoxControlElement)

        End Get
    End Property
    Protected Overrides Function CreateViewElement() As TextBoxViewElement
        Return New MyWrapPanel

    End Function
End Class

Class MyWrapPanel
    Inherits TextBoxViewElement

    Protected Overrides Function InsertTextBlocks(index As Integer, text As String, blockType As Type) As Integer

        If String.IsNullOrEmpty(text) Then
            Return index
        End If

        Dim textBuilder As New StringBuilder()

        For i As Integer = 0 To text.Length - 1
            Dim symbol As Char = text(i)

            If Char.IsWhiteSpace(symbol) OrElse symbol = TextBoxViewElement.TabSymbol OrElse symbol = TextBoxViewElement.LineFeedSymbol OrElse symbol = TextBoxViewElement.CarriageReturnSymbol Then
                If textBuilder.Length > 0 Then
                    Dim textBlock As ITextBlock = Me.CreateBlock(textBuilder.ToString(), blockType)
                    If index >= Me.Children.Count Then
                        Me.Children.Add(TryCast(textBlock, RadElement))
                        index = Me.Children.Count - 1
                        textBlock.Index = index
                    Else
                        textBlock.Index = index
                        Me.Children.Insert(index, TryCast(textBlock, RadElement))
                    End If

                    textBuilder = New StringBuilder()

                    index += 1
                End If

                Dim tabBlock As ITextBlock = Me.CreateBlock(symbol.ToString(), blockType)
                tabBlock.Index = index
                Me.Children.Insert(index, TryCast(tabBlock, RadElement))
                index += 1
                Continue For
            End If

            textBuilder.Append(symbol)
        Next

        If textBuilder.Length > 0 Then
            Dim textBlock As ITextBlock = Me.CreateBlock(textBuilder.ToString(), blockType)
            textBlock.Index = index
            Me.Children.Insert(index, TryCast(textBlock, RadElement))
            index += 1
        End If

        Return index - 1
    End Function
End Class

Please refer to the attached sample project and attached gif file which illustrates the desired behavior when RadForm1 is run. If you run RadForm2 which uses RadDropDownList, the binding doesn't work as expected.

Workaround:
this.radDropDownList1.SelectedIndexChanged += RadDropDownList1_SelectedIndexChanged;
this.radDropDownList1.DisplayMember = "Naziv";
this.radDropDownList1.ValueMember = "Id";
this.radDropDownList1.DataSource = bs;

private void RadDropDownList1_SelectedIndexChanged(object sender, 
    Telerik.WinControls.UI.Data.PositionChangedEventArgs e)
{
    if (e.Position > -1)
    {
        Roditelj parent = this.radDropDownList1.SelectedItem.DataBoundItem as Roditelj;
        this.radDropDownList2.DataSource = null;
        this.radDropDownList2.DisplayMember = "Naziv";
        this.radDropDownList2.ValueMember = "Id";
        this.radDropDownList2.DataSource = parent.Djeca;
    } 
}

Please refer to the attached sample project and try to open the form's designer. If you comment  [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)] for the EditarTextBox property (typeof(RadTextBox)), clean and rebuild, the designer is opened as expected.

Workaround: use RadTextBoxControl.

How to reproduce:
 this.radMaskedEditBox1.Font = new System.Drawing.Font("Segoe UI", 20F);

 this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Standard;
 this.radMaskedEditBox1.Mask = "#####-######";
 this.radMaskedEditBox1.Value = "47997006886";


Workaround: 
this.radMaskedEditBox1.Font = new System.Drawing.Font("Segoe UI", 20F);

this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Standard;
this.radMaskedEditBox1.Mask = "#####-######";
this.radMaskedEditBox1.Text = "47997006886";

To reproduce:
- Add text that contain multiple blank lines to a textBox
- Set SpellCheckMode to AllAtOnce 
- Perform a spell check.