We just posted a new WPF Studio build that addresses a measure issue found in the build 504 SyntaxEditor completion list. It also updates the completion list to auto-resize the width based on current items in the list when filters are applied.
RibbonWindow received a number of changes to make it function and look better in Windows 7. DataGrid got a minor Aero theme tweak and Editors got a small bug fix.
The new build is now live.