I am using the WPF 3.5 binaries of version 22.214.171.124 of the Extended WPF Toolkit. Let me begin by thanking you, Brian, for putting all the effort into this project. You have plugged a huge void.
With this instance of the DateTimePicker control:
<DockPanel Name="ToDateTimePanel" DockPanel.Dock="Left">
<extToolkit:DateTimePicker Name="dtPickTo" Height="Auto" MinWidth="130"
there appears to be an issue with positioning of the text. Note that the descenders on the lower-case characters are missing:
Of course, this isn't a problem if I stick to a date format that is all numeric!