Photoshop CS3 upgrade

I know Photoshop since the earlier days. Not that early ! .. the foundation was created by 2 brothers in 1988 by creating a piece of Software for Macintosh Plus called Display, later ImagePro and finally renamed in Photoshop. PS 1.0 was released in 1990. Fast forward.... I am using it on a more professional level since about 10 years and bought the last version (CS) in 2004. So far I did not see why I should upgrade to CS2 or CS3 (released in 2007), but more and more plugins, tutorials and books are referring at least to CS2 now, so I invested 340.- SGD in the Windows upgrade. Today I also would consider GIMP (if start again),even most of the functionality I use, is to do basic photographic touchup, but I stick to PS and I am happy with it. One of the few software that maintains a very good reputation and does not disappoint you with crashes and blue screens.
Links: Photoshop (Adobe), History of Photoshop in Wikipedia, GIMP