ReSharper 1.5 Released! Includes New Refactorings
Recently, I was trying to write some code on a coworker's computer and kept hitting funky key combinations that had no meaning on his machine since he didn't have this installed. I had to actually type out a bunch of code that just spills out when using this add-in. It felt so stone age.
Just to be complete, I know many are fans of CodeRush for Visual Studio. I liked it enough, but the lack of Refactoring support was a problem for me, which is why I chose ReSharper.