As time passes, I wonder more and more why everybody is waiting for Aperture 4 (me too :-/)? A new version generally means new bugs, often a handful new "features" nobody really needs, sometimes a new version predicts a different workflow which is not always better than before. And every time you have to pay for an upgrade.
The only thing I really miss in Aperture is a distortion correction tool (I think I mentioned earlier): one simple slider to adjust pincushion and barrel distortion and maybe another tool for basic perspective corrections (well knowing that using a PC lens could do the trick much better).
Apart from that, Aperture 3.3.2 is absolute perfect for me. The update from 3.2.4 has been some kind of awakening. It's much faster now, uses remarkably less memory than before and since the update I didn't saw a single crash! That's what I really expect from a professional software. Nothing more, nothing less.
For some extended image processing I use GIMP (on OSX/X11). It offers most of the features Photoshop does, but for free!