CS3 is nice, and a definite step-up from CS2. Most of the extra features fall into categories that texture artists will fawn over, thanks to a variety of new plug-ins, and built-in support for 3DS Max and Milkshape Pro. One point that really irritates me is that it demands more of my computer than CS2, forcing me to dump 1.8gb of RAM to make creating new images take under 10 seconds.
Also, Adobe has upped the security yet again, with probably the most comprehensive coding behind its serial numbers used today. It ain't no ROT13, that's for sure, and from the brief research I did on the subject for a nerd-essay, it seems there aren't too many successful hacks on the market, probably thanks to more legal downloads and a much larger database needed to work from. As surprised as I am to say this, Adobe seems to be curbing illegal copies quite efficiently this time around, although I'm sure that if you looked hard enough, you'd find something eventually.