I still use cs2. I tried out a trial of a newer one once, and was confused by a few slight differences so I gave up and haven't ever upgraded. I would like to get a newer version someday, but right now, I don't think i need it...
I think CS2 is a pretty good product. I've used CS2, CS3 and CS5. I had to upgrade to CS5 when I converted to a MAC. I actually liked CS2 quite a bit. If you have the $$ to upgrade, you might just try out a trial version to see if the new features are worth it to you. Good luck!