Workaround: custom RadGridViewDragDropService and an override of the HandleMouseMove method, please check the attached project

To reproduce:
void radGridView1_CellValueChanged(object sender, Telerik.WinControls.UI.GridViewCellEventArgs e)
{
    if (e.Value == null || e.Value == DBNull.Value)
    {
        e.Row.Delete();
    }
}
-  Use the enter key to confirm the change


Workaround:
void radGridView1_CellEndEdit(object sender, Telerik.WinControls.UI.GridViewCellEventArgs e)
{
    if (e.Value == null || e.Value == DBNull.Value)
    {
        e.Row.Delete();
    }
}

Please refer to the attached sample project and follow the steps illustrated on the attached gif file.

Workaround: subscribe to the CellBeginEdit event and focus the grid:

public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
        this.radGridView1.CellBeginEdit += radGridView1_CellBeginEdit;
    }

    private void radGridView1_CellBeginEdit(object sender, GridViewCellCancelEventArgs e)
    {
        this.radGridView1.Focus();
    } 
}

To reproduce:
- Create a new Visual Studio project with a single form.
- Add a RadGridView control to the form.
- Add a child Template to the RadGridView.
- In the properties of this child template, enable AutoExpand Groups.
- Close the form editor and re-open.

How to reproduce:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.radGridView1.DataSource = this.GetData();
        this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
        this.radGridView1.RightToLeft = System.Windows.Forms.RightToLeft.Yes;

        foreach (var col in this.radGridView1.Columns)
        {
            col.HeaderTextAlignment = ContentAlignment.MiddleLeft;
        }
    }

    private DataTable GetData()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("Date", typeof(DateTime));
        dt.Columns.Add("Bool", typeof(bool));
        dt.Columns.Add("Bool1", typeof(bool));
        dt.Columns.Add("Bool2", typeof(bool));
        for (int i = 0; i < 50; i++)
        {
            dt.Rows.Add("Name " + i, DateTime.Now.AddMinutes(i), i % 2 == 0 ? true : false, false, false);
        }

        return dt;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        this.radGridView1.PrintPreview();
    }
}



Workaround: 

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.radGridView1.DataSource = this.GetData();
        this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
        this.radGridView1.RightToLeft = System.Windows.Forms.RightToLeft.Yes;
        this.radGridView1.PrintCellFormatting += radGridView1_PrintCellFormatting;

        foreach (var col in this.radGridView1.Columns)
        {
            col.HeaderTextAlignment = ContentAlignment.MiddleLeft;
        }
    }

    private void radGridView1_PrintCellFormatting(object sender, PrintCellFormattingEventArgs e)
    {
        if (e.Row is GridViewTableHeaderRowInfo && this.radGridView1.RightToLeft == System.Windows.Forms.RightToLeft.Yes)
        {
            e.PrintCell.TextAlignment = ContentAlignment.MiddleRight;
        }
    }

    private DataTable GetData()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("Date", typeof(DateTime));
        dt.Columns.Add("Bool", typeof(bool));
        dt.Columns.Add("Bool1", typeof(bool));
        dt.Columns.Add("Bool2", typeof(bool));
        for (int i = 0; i < 50; i++)
        {
            dt.Rows.Add("Name " + i, DateTime.Now.AddMinutes(i), i % 2 == 0 ? true : false, false, false);
        }

        return dt;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        this.radGridView1.PrintPreview();
    }
}

To reproduce:
- Add a grid to a split panel.
- Edit a cell and resize the panel without ending the edit.
- Click back in the same cell.

Workaround:
private void RadGridView1_CellEditorInitialized(object sender, GridViewCellEventArgs e)
{
    BaseGridEditor editor = e.ActiveEditor as BaseGridEditor;
    var element = editor.EditorElement as RadTextBoxEditorElement;
    if (element != null)
    {
        element.TextBoxItem.HostedControl.LostFocus -= HostedControl_LostFocus;
        element.TextBoxItem.HostedControl.LostFocus += HostedControl_LostFocus;
    }
}

private void HostedControl_LostFocus(object sender, EventArgs e)
{
    this.RadGridView1.EndEdit();
}

Workaround: Inherit the GridViewSearchRowInfo and override the SelectNextSearchResult method
class MyGridViewSearchRowInfo : GridViewSearchRowInfo
{
	private GridViewInfo gridViewInfo;
	private RadGridView radGridView;

	public MyGridViewSearchRowInfo(GridViewInfo gridViewInfo, RadGridView radGridView) 
               : base(gridViewInfo)
	{
		this.radGridView = radGridView;
	}

	public override Type RowElementType {
		get { return typeof(GridSearchRowElement); }
	}

	public override void SelectNextSearchResult()
	{
		if (this.radGridView != null) {

			this.radGridView.ElementTree.Control.Invoke(() => { base.SelectNextSearchResult(); });
		}
	}

}

To reproduce:
- Add textbox and checkbox columns to a grid the checkbox column should not be visible without scrolling to the right.
- Change the data source in the FilterChanged event.
- Test this by moving the checkbox column in front of the text box column.
 

To reproduce:

1. Add a UserControl and drop a RadGridView in it.
2. Use the following code:

public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
        ColumnGroupsViewDefinition view = new ColumnGroupsViewDefinition();
       
      this.radGridView1.ViewDefinition = view;
        
        view.ColumnGroups.Add(new GridViewColumnGroup("Group"));
        view.ColumnGroups[0].Rows.Add(new GridViewColumnGroupRow() );
        GridViewTextBoxColumn col = new GridViewTextBoxColumn("Col1");
        this.radGridView1.Columns.Add(col);
        view.ColumnGroups[0].Rows[0].ColumnNames.Add("Col1");           
    }
}

3. Drag the UserControl from the Toolbox to the form.

Workaround: set the ViewDefinition property after all columns are added.

Workaround: check the attached project

To reproduce:
- Assing context menu using one of the default properties.

Introduce a property to change symbol used to separate summaryItems in SummaryRowGroupHeaders.

To reproduce:
GridViewHyperlinkColumn col = new GridViewHyperlinkColumn();
col.FieldName = "Name";
col.HyperlinkOpenAction = HyperlinkOpenAction.DoubleClick;

Workaround:
Use the CellDoubleClick event:
void radGridView1_CellDoubleClick(object sender, GridViewCellEventArgs e)
{
    if (e.Column is GridViewHyperlinkColumn)
    {
        string hyperlink = e.Value.ToString();
    }
}

To reproduce
- Add condition formatting object that changes the font.
- Add cell style that changes the background only.

Workaraound:
Use the CellFormatting event instead of a style.

For now you can manually add the columns to the ExcelFilteredColumns collection when the filters are added in code:

FilterDescriptor fd = new FilterDescriptor("Value", Telerik.WinControls.Data.FilterOperator.IsEqualTo, "B");
fd.IsFilterEditor = true;
radGridView1.FilterDescriptors.Add(fd);

this.radGridView1.MasterTemplate.ExcelFilteredColumns.Add( this.radGridView1.Columns[0] );   

How to reproduce: 
Public Class Form1
    Sub New()

        InitializeComponent()

        Dim col As New GridViewTextBoxColumn("Column1")
        Me.RadGridView1.Columns.Add(col)
    End Sub

    Private Sub RadButton1_Click(sender As Object, e As EventArgs) Handles RadButton1.Click
        Dim sw As New Stopwatch
        sw.Start()

        Me.RadGridView1.Rows.Clear()
        Me.RadGridView1.BeginUpdate()
        Dim RowInfo
        For ii = 1 To 100000
            RowInfo = Me.RadGridView1.Rows.AddNew
            RowInfo.Cells("Column1").Value = ii
        Next
        Me.RadGridView1.EndUpdate()

        sw.Stop()
        Console.WriteLine("Elapsed: " & sw.Elapsed.TotalSeconds)
    End Sub
End Class

Workaround: add data to a collection and use bound mode

1 .Add RadgridView to Form
2. Set "AllowSearchRow" property to True
3. Add a row and place the word "Gießen" (name of a city) in a column
4. When the program is running type "Giessen" in the AutoSearch Row. After the "n" an ArgumentException 
is thrown.

To reproduce:

public Form1()
{
    InitializeComponent(); 
    List<Item> items = new List<Item>();
    items.Add(new Item(1,"sample"));
    items.Add(new Item(2, null));
    items.Add(new Item(3, "sample2"));
    this.radGridView1.DataSource = items;
    this.radGridView1.AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill;
    this.radGridView1.EnableFiltering = true;
    this.radGridView1.ShowFilteringRow = false;
    this.radGridView1.ShowHeaderCellButtons = true; 
}

public class Item
{
    public int Id { get; set; }

    public string Description { get; set; }

    public Item(int id, string description)
    {
        this.Id = id;
        this.Description = description;
    }
}

Workaround: If possible, instead of using null value, use empty string.
If not possible, you will have to employ 3 classes - MyFilterMenuTreeElement, MyFilterMenuTreeItem, MyListFilterPopup. The classes are provided in the attached project RadGridViewFiltering.zip. Once you add the classes to your project, all you have to do is to replace the default popup with the new one, in the FilterPopupRequired handler: 
		private void RadGridView1_FilterPopupRequired(object sender, FilterPopupRequiredEventArgs e)
        {
            if (e.FilterPopup is RadListFilterPopup)
            {
                e.FilterPopup = new MyListFilterPopup(e.Column);
            }
        }
		
The approach is also demonstrated in the attached project.