The Header property setting is replaced with a default value when the RadVirtualKeyboardWindowAutomationPeer is created. This happens on environments where the automation peers creation kicks-in. Like, on touch devices, when a screen narrator application is used, on visual elements inspection with some tools (like UISpy or Snoop) or any other automation testing that requires automation peers. 

In that case, instead of the user defined Header value, the window's header is replaced with "RadVirtualKeyboardWindow" string.

To work this around, disable the automation peers:

public partial class App : Application 
{ 
    public App() 
    { 
        AutomationManager.AutomationMode = AutomationMode.Disabled; 
        this.InitializeComponent(); 
    } 
} 

Our company would like to use in a greenfield project this new UI component.

On our machine, in both our sample projects and even running your official WPF Demo App, the virtualkeyboard component does not render its buttons correctly.

This is our sample xaml:

<Window x:Class="TelerikWpfApp1.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" Height="350" Width="525">
        <Grid>
        <telerik:RadVirtualKeyboard DefaultKeyboardLayout="Compact" HorizontalAlignment="Stretch" />
    </Grid>
</Window>

In the attachment you can see how the virtualkeyboard renders ootb. Are we missing something?