I'm still using CS2 here, and CS4 is coming out? But, seriously, what more features can I possibly want? All I ever used were the layers, the blending modes, the brushes, the eraser, the smudge tool, the selection tools, and dodge and burn tools, and the eyedropper. And some really basic filters. These has been around since Photoshop 6 or something.
Unless CS4 comes with some kind of brain sensor that alows me paint something just by thinking about it, I am not buying it!