That's the question I'm asking myself, too. They added a lot of functionality to VS (unit testing, TFS support etc.), but they never added more refactorings, which I and surely others would appreciate. ReSharper's refactoring functionality is right now the only reason I would consider to install the add-in, but since I didn't need any of the advanced refactorings yet, I'm keeping ReSharper away from my VS installation. I get my work done without it, so I see no need to bloat VS any more :) But, I surely can recommend to install it for various other reasons, e.g. I stumbled upon a few interesting things thanks to its suggestions.