Adobe are after your cash again, a new updated photoshop will be available on the 21st/22nd of this month.
You can check out some of the improvements here:
As with the last 3 versions there are worthwhile improvements for high end creative retouching with smaller improvements for the kind of minimal retouching regime of say wildlife photographers.
Content aware fill will reduce the retouching time on creative work whilst the improved camera raw will be more generally useful.
CS5 is 64bit on Apple Macs for the first time so if you are running a recent Mac this may tip you over into making the purchase.
Prices are up on last time, I think Adobe assume everyone will gladdly pay even more, I will be updating because I need to (teaching/retouching work). If your happy with what you have then dont worry about the upgrade.