The current workaround is to set the FontSize of the underlying RadComboBox explicitly:

		<Style x:Key="RedCellStyleStyle" TargetType="telerik:GridViewCell" >
			<Setter Property="FontSize" Value="25" />
			<!--workaround-->
			<Style.Resources>
				<Style TargetType="telerik:RadComboBox">
					<Setter Property="FontSize" Value="25" />
				</Style>
			</Style.Resources>
		</Style>

Currently I am using row selection for my readonly grid. There is a cell highlight that shows which cell the user has selected.  I would like to disable that highlight so that the row selection looks consistent no matter where on the row the user clicks.
(Copied from: 
http://www.telerik.com/forums/disable-selected-cell-highlight

See this link for more details:  http://www.telerik.com/forums/how-to-remove-focus-rectangle-from-selected-cell#9GAEx-HPN0C_qOGAsXY2PA   )

This should be possible without adding 200 lines xaml code. Just expose the CellBorderBrush Property so we can easily set it to transparent

Grouping of columns in RadGridView by using a ColumnGroupDescriptor in XAML does not work when ShowGroupPanel is set to False and there is a RelativeSource binding in the ColumnGroupDescriptor.

Check Demos >> GridView >> Hierarchy

First HeaderCell should be aligned with the first cell in the gridview. You can find a screenshot attached. 

The performance of the RadGridView scrolling diminishes significantly when the grid has thousands of rows and alternating row styles are used.  This causes scrolling to be virtually unusable.  I note this is a known limitation of the RadGridView from information from https://docs.telerik.com/devtools/wpf/controls/radgridview/troubleshooting/performance 

We have had to remove the alternating row styles from our current product while porting to the RadGridView.  I am requesting if this issue is going to be fixed in the future anytime soon.