This is actually really easy as long as every developer on your project makes the move simultaneously. If not, well, there are a couple of things to keep in mind.
VS2008 will convert your solution and project files even when you stay in .Net 2.0. Converted solution files can not be opened by VS2005. Project files can still be opened (you’ll get a warning but that is all). This means you’ll have to work with two versions of your .sln files, one for VS2008 and one for VS2005.
If you’ve used Microsoft’s Test Project template for writing unit test etc, the reference to ”Microsoft.VisualStudio.QualityTools.UnitTestFramework” will have changed in the conversion, breaking the project for VS2005. This reference will have to be manually changed back and forth depending on what VS version developers use.
That’s it so far, but I’m sure there are some other pitfalls out there waiting for me 😛