Besides the UI improvements, esp. for ASP.Net developers,
http://wiki.asp.net/page.aspx/134/orcas/
you might want to check out this video (16 minutes):
http://channel9.msdn.com/ShowPost.aspx?PostID=328382
Even if you are still targeting CLR 2.0, you can still take
advantage of many of the improvements in the IDE.
I once tried upgrading a 150,000-line project from VS2005
to VS2008 and I could continue working on it (targeting
CLR 2.0) and compile it without any problems.
There is an SP1 on the way for VS2008:
http://msdn.microsoft.com/en-us/vstudio/products/cc533447.aspx
For ASP.Net developers it should be a no-brainer. For small,
client-only WinForms applications, not so sure. In a team
environment where everybody is not ready to make the
jump, maybe not a good idea either.
But "definite advantages" is a relative term and depends
on where you are now and what you want to do.
Regards,
Joergen Bech