Sorry, this would entail that we maintain two code bases and it would make it much more difficult to keep things in sync.  There is really nothing that should prevent you from going to VS2008 since all of your existing projects will work...without chaning a single thing!  They have done a beautiful job with VS2008 and it is a much better environment to work within.  If you can, I recommend moving forward.

I'm not sure if this is the right place to ask, but could there be a VS 2005 version of the source code projects?