<p>Could somebody please name a few.  I could given time, but this is for somebody else, and I'd also like some community input.</p>

Depends on your programming language.
On .net, the built-in support for .net 3.5 is obvious, although this is mainly project templates. However, SP1 adds .net Client Framework support, which is not possible within VS2005 to my knowledge.
This also means support for WPF with a XAML Designer, although most people still prefer Expression Blend for WPF Interfaces.
Apparantly, there is now a JavaScript Debugger, even though it's a
bit broken
as it seems (not sure if SP1 fixes this)
In short: For .net 3.5, it's almost a must-have if you are a professional developer, but that is just my opinion.