Downloaded, running, looking at the walk throughs, here are some of the things I've seen so far.
- Customisable Start page in XAML (don't know if I'd bother)
- Zoomable code editor (I bet this was a feature request from MS evangelists)
- Highlight current line in editor (YES! the SlickEdit addin slowed my machine horribly. However, I haven't yet managed to get it to work in the CTP)
- Stuff for hooking into editor and adding your own formatting, highlighting, intellisense, smart tags etc. (Don't think I'll be needing that any time soon)
- Call Hierarchy - tree view of who calls your method and who your method calls
- Static type 'dynamic' - strictly speaking this is C#4.0, not VS2010 (watch the PDC Future of C# talk by Anders to get some of that Wow factor)
- Generate from usage: This is so cool, you write your test, then use VS refactoring to create all of the boilerplate class/property/method definitions for your code. (And you can generate an entire class from an anonymous class!)
- Quick search - (equivalent of Code Rush Ctrl Shift Q)