The VS2005 SDK Needs A Lot Of Work
Have you ever tried to build an addin for Visual Studio? I'm working on one right now, and it's not much fun. I was hoping the VS2005 SDK (formerly VSIP) would be a bit more user-friendly than the previous versions... but I was wrong.
Microsoft should really take a look at Jamie Cansdale's ManagedAddin Framework. He's done a great job of making it dirt simple to write an add-in. Hopefully Jamie will update his code to run on VS2005.