...I'd like to see SlickEdit on Mac and Windows make me just as productive as if I was using Visual Studio 2010 and ReSharper 6.1, but for other languages...
ReSharper's code and styling support is extremely cool! +1 from me.
Additionally an improved (incremental) upgrade concept would be great. I find it a little bit annoying having to install a completely new software package with every new release.