Whidbey project converter
Language enhancements aside, the VS.NET Whidbey IDE will definitely be a productivity enhancer. Chances are Microsoft won't support building to older versions of the framework with the new IDE, especially as “defaults“ like partial classes make their way into newer releases.
Unfortunately, not everyone will be able to force their customers to upgrade to a(nother) new version of the runtime, so some of us will be stuck in VS.NET 2003 for a while. The good news is that it should be possible, with a little elbow grease, to use the new IDE and produce 1.x code. Time will tell as things evolve.
In the meantime I've written a very simple (no error handling, etc.) Whidbey -> VS.NET 2003 C# project file converter. (Whidbey does a nice job of converting 2003 files, so I didn't bother with that.) It only generates a VS.NET 2003 C# project file, so you're out of luck if you use any of the new language features and try to compile in 2003. I really want to use this IDE for “real“ work ASAP, so I'll be doing whatever I can to make that possible if it looks like we can't go to v2 in a reasonable amount of time.
You can download it here.