For the last week (at my new gig) I've been using ReSharper 3.0, and I must say I'm pretty darned impressed.  I hadn't looked at ReSharper since the very early versions, and had sort of written it off in favor of CodeRush/Refactor, but ReSharper 3 has some pretty compelling features...

• ReSharper parses your code outside of the compiler, and therefore knows stuff the compiler couldn't, like when you reference something in another namespace without the proper using directive in place, and ReSharper figures out which namespace you mean, and asks if you'd like to add the reference.  Slick.
• Inline suggestions.  ReSharper parses your code and offers up both errors (in an easier way the VS.NET, IMHO) and suggestions, such as "you really could make this field readonly".  These errors and suggestions are also displayed in a sidebar next to the scroll bar as red, green or yellow lines, so you can scroll the the problems quickly.  Nice.
• Integrated NUnit support.  I love the way ReSharper handles NUnit integration.  You get little buttons in the right hand sidebar (where your breakpoints show up) that allow you to run or debug individual tests or the whole fixture.  The results get put in a custom results pane, much neater than the text based report you get from TestDriven.NET.  If you happen to have JetBrains profiler, that's integrated as well. 
• Clever autocompletion.  I know I probably shouldn't be so impressed with this one, but just this morning I wrote a line that returned an IEnumerable, then on the next line typed foreach, and it completed the whole block, figured out the right types, etc.  Very clean.
• Nice refactoring support.  I haven't had too much time to play with this yet, but it looks like it supports a goodly number of refactorings.  Cool.

I'm looking forward to playing with it more in the days to come.