Cs4 is better mate, at least for me. I make a lot of tutorials and thus my canvas is pretty big each time and I switch a lot between .psd files. In Cs3, when you switch, you're always taken back to the top part and you always have to scroll back to where you were, annoying as hell. So I'm gald that got fixed when I switched to Cs4
PDF About Photoshop CS4 Click the link, it goes to a .pdf that shows when Adobe announced it and what are some of the features.
CS4 is better of course as it's the latest one from Adobe and like the rest of the members said in this thread, it's a lot more easier to use and has less problems compared to the CS3.
The new layout etc. is major, MAJOR. Camera Raw got a lot of new good features. Mask's got a lot better. As did Adjustments etc. Content Aware Scaling is fairly huge. Protect tones when Dodging/Burning Preview when clone stamping Auto align layers etc. And, more. As a siggie...person, it's not that huge of an update, but the layout on it's own makes it worth getting hold off over CS3.