We're starting to use Windows 7 64bit for Developer Desktops (well, three of us so far that are willing to be early adopters).
One of the things we had a problem with was logging into a Citrix remote-desktop; it would give the user a "CDViewer has stopped working". Here are the diagnostics:
Problem Event Name: CLR20r3 Problem Signature 01: cdviewer.exe Problem Signature 02: 126.96.36.199560 Problem Signature 03: 4aac18be Problem Signature 04: DesktopViewer Problem Signature 05: 188.8.131.52560 Problem Signature 06: 4aac18ba Problem Signature 07: 105 Problem Signature 08: 80 Problem Signature 09: System.IO.InvalidDataException OS Version: 6.1.7600.2.0.0.256.48 Locale ID: 1033
It has something to do with the version of Citrix that we're using on the server vs. the latest client version. The workaround is rather simple, in Windows 7 you need to associate the ".ica" extension with C:\Program Files (x86)\Citrix\ICA Client\wfica32.exe program.