I currently have a project completely working and it runs on the Panda II with an XBee for communication. Now I see the FEZ Cerbuino Bee which has the XBee port built into it (beautiful design IMNSHO). So, the question is, how hard is it to migrate from the Panda II to the gadgeteer stuff? I know going from a Panda II to a Mini or reverse is quite easy, just change the DLL you include and double check your IOs, but is it just as easy to go from Panda II to gadgeteer?
From what I understand, not all features are available (yet), like virtual USB com ports. Maybe if you tell us more on what hardware is connected someone can help you decide.