Photoshop CS, CS2, CS3 have their differences especially when you export your files, there are added features Like Zoomify. I like this stuff. Anyway, there's nothing more new. I wish Macromedia didn't merged with Adobe.
I can agree with that but if Macromedia was going bankrupt, what else could the poor suckers do? *sigh*
Anyhow, I don't use CS3, I imagine it consumes a lot of RAM considering all those new upgrades. Anyone can testify to the fact that Adobe programs get greedier and greedier on the RAM consumption with each new version update.
I've actually got the complete platinum software, but the entire thing just takes too much of my space. I installed it and there was a problem, as the software didn't install properly. After going to remove and re-install, I noticed all the space the entire lot took up, something over 900MBs I remember. So I just decided to un-install and stick with the old. I don't think I'm just yet missing out on anything. As I can still design some good old graphics with my current CS. I reckon I wouldn't really need all those added features from CS3 anyhow.
I suppose to answer the thread question without actual first hand knowledge, I'd say go for CS3 if you are going to gear towards 3D design, because from what I hear, that's what the main updates include.