Use the new implict mechanism. Attach the Windows8 _Wpf project instead of Windows8 dll. Xaml parse exception occurs runtime - 
"Cannot set unknown member 'Telerik.Windows.Controls.MaskedInput.PreviewInputTextBox.IsReadOnly'."

Note: you can try the workaround added here: http://stackoverflow.com/questions/6850713/weird-xaml-parsing-error-when-trying-to-set-textbox-isreadonly

Numeric input with  Mask="#7" or CurrencyInput with       Mask="c7" .

 UpdateValueEvent="LostFocus"

Value =3000

If you remove the digit "3" with backspace / delete and then type digit 4,  You will receive value"4" and text "0004".

The expected result is Text="4000" and value =4000.

Workaround:  Use Mask="" (no-mask).
=============
Fixed in R3 2016.

When you set the IsCurrencySymbolVisible to false and Mask="1.x" you are not able to fill the first digit. 
For example if you want to insert 1.234 and you press 1 the control fills 0.001 and all other digits can be added at the last position only.

When two or more MaskInput controls are focused at the same time, the application freezes.

Workaround:

Instead of 

  txtMask1.Focus();
  txtMask2.Focus();

Use

  txtMask1.Focus();
                Dispatcher.BeginInvoke(new Action(() =>
                    {
                        txtMask2.Focus();
                    }), DispatcherPriority.Loaded);

When using implicit styles mechanism and you merge Telerik.Windows.Controls.Input an exception is thrown.

If the XAML file is set with BUILD ACTION PAGE the issue is not reproducible.

Another workaround is to reference dlls only, not xaml theme files.

Issue is reported in several msdn / stackoverflow threads and it appears to be an MS-TextBox one. 
http://stackoverflow.com/questions/6850713/weird-xaml-parsing-error-when-trying-to-set-textbox-isreadonly 

Mask is "a-a". Value is set to "M-M".

The MaskedTextInput control must internally coerce the Value to "MM".
Instead , MaskedTextInput'Value is "M-" which is wrong.

Other example of the same issue:
Bound Value is bbaabbaabbdd, Mask is "aa-aa-aa-aa-aa-aa"
The result is - value becomes bbbbbbddaaaa.

Workaround:
Use custom Mask Token (check help article: http://docs.telerik.com/devtools/wpf/controls/radmaskedinput/how-to/howto-create-custom-token.html)

 public class CustomToken : ITokenValidationRule
    {
        public bool IsRequired
        {
            get { return false; }
        }

        public bool IsValid(char ch)
        {
            return ValidChars.Contains(ch.ToString());
        }

        public char Token
        {
            get { return '$'; }
        }

        public TokenTypes Type
        {
            get { return TokenTypes.AlphaNumeric; }
        }

        private string myValidChars = "0123456789qwertyuioplkjhgfdsazxcvbnm";
        public string ValidChars
        {
            get { return myValidChars; }
        }
    }

    TokenLocator.AddCustomValidationRule(new CustomToken());
            InitializeComponent();

   <telerik:RadMaskedTextInput Mask="$-$"  

In PreviewKeyDown we change the Foreground of the MaskedInput when the Key is Return. Then we revert the color on other key press. Changing the focus returns the color set on Return but it shouldn't.

In NoMask scenario the Placeholder should not be a valid property. The issue: if the Placeholder is an underscore (default value) and the user's input underscore this character is not displayed on lost focus.


Workarounds: 

1. Set empty string for Placeholder (Placeholder="")

2. Set TextMode property to MaskedText (TextMode="MaskedText")

The workaround is to create a custom class which derives from RadMaskedTextInput and override the OnSelectionOnFocus() method.

 protected override int OnSelectionOnFocus(SelectionOnFocus selectionOnFocus)
        {
            if (MaskedInputExtensions.GetCaretToEndOfTextOnFocus(this))
            {
                return this.Text != null ? this.Text.Length : 0;
            }
            if (selectionOnFocus == SelectionOnFocus.Default)
            {
                return 0;
            }
            return base.OnSelectionOnFocus(selectionOnFocus);
        } 
Then you can set the following properties to the mask:
 -  TextMode="PlainText"
 -  Placeholder=" "
 -  maskedInput:MaskedInputExtensions.CaretToEndOfTextOnFocus="True"

Change the x:Key of the PreviewInputTextBox style in all themes definitions as at the moment it matches the x:Key of the TextBox style in the System.Windows.xaml.

This is completed in R2  / R3 2013.

If you enter the placeholder character in a MaskedInput, it will be processed as an empty position. And if the InsertBehavior is Input, the positions containing the placeholder chars will be overriden if the user keeps entering characters after the end of the allowed input is reached.

The Value property of the TextInput is not correctly updated when using the On-Screen Touch keyboard when using no mask (Mask=""). We managed to reproduce the issue on Windows 8.1, 10. The behavior is different in both Windows OS. To get the Touch Keyboard you can check the following link.

Windows OS  8.1 - When you enter text and pressed backspace key- the value property is not updated the first time.

Windows OS 10 - When you enter text and pressed backspace key the value property is updated correctly. But if you HOLD THE BACKSPACE KEY the Value property ignored this behavior.

In MaskedTextInput the ClearButton will make the Value "" but it should make it NULL. All other InputControls have null value after pressing ClearButton.

No-masked TextInput works fine - the ClearButton makes the Value Null.

As a workaround, you can use the ClearCommand, bind it to Command from your ViewModel and the execute handler can set the bound Value to null.

Setting the Extnesions Minimum and Maximum values restricts the input of values that fall in the designated area but that start with a digit lesser than the minimum value. For example in the MaskedNumeric/CurrencyInput, if you set MaskedInputExtensions.Minimum="2" and MaskedInputExtensions.Maximum="20", you can't enter 12 unless the current value is 2 and the cursor is positioned before the 2 - only then you can insert the digit 1 before the digit 2 to create an input of 12.

Bug details:
OS: Windows 10.
VS: 2015 professional
Telerik version: 2015.2 SP1

Code sample:
<Window x:Class="RadMaskedInputBug.MainWindow"
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
                Title="MainWindow">
    <Grid>
        <telerik:RadTextTimeInput />
    </Grid>
</Window>


The designer crashes and shows only the exception:
InvalidOperationException: Can only base on a Style with target type that is base type 'RadMaskedTextInput'.

UPDATE: 
Telerik has submitted a bug report to Microsoft. You can check its progress here: https://connect.microsoft.com/VisualStudio/feedback/details/2005303/designer-error-can-only-base-on-a-style-with-target-type-that-is-base-type-customcontrol-when-a-style-is-basedon-a-style-of-an-abstract-class 
On 21/12/2015 Microsoft commented that a fix has been submitted and will be available in the next update.

Available in LIB version: 2016.3.1010

Possible workaround:
You can subscribe to the PreviewTextInput event of the control and change the position of the caret if the typed char is the same as the current one.

private void RadMaskedTextInput_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            var input = sender as RadMaskedTextInput;
            var currentPosition = input.SelectionStart;

            if (currentPosition != input.Text.Length)
            {
                var currentChar = input.Text[currentPosition];

                if (currentChar != input.Placeholder && currentChar.ToString() == e.Text)
                {
                    input.SelectionStart++;
                }
            }
        }



Available in R3 2016 Release

In MaskedNumericInput when Mask="p2" you can not delete/replace the minus "-" sign when you select all and type a digit.

With no-mask, select all then typing a digit will remove the negative sign symbol from the text.

As a workaround, users can use Mask="", FormatString="p0" and maskedInput:MaskedInputExtensions.Maximum="0.99".

Second Workaround:

<telerik:RadMaskedNumericInput Mask="p2" Value="-0.25" x:Name="input" PreviewKeyDown="MaskedInput_PreviewKeyDown"/>

        private void MaskedInput_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            string keyString = e.Key.ToString();
            if (keyString.StartsWith("D") && keyString.Length == 2)
            {
                if (this.input.SelectionLength == "-AA %".Length)
                {
                    this.input.ClearCommand.Execute(null);
                }
            }
        }

Edit: Actually this is default behavior for NumericIinput with default Masks #9.2. Select All on negative value then pressing digit does not remove the negative sign.
This is the reason we will mark this bug as Declined. Please use some of the mentioned workarounds.
Please submit a support ticket via our ticketing system if this feature is critical for your business requirement.