I spent a year playing with Photoshop CS2 before getting Photoshop CS3. CS3 doesn't take up as much computer space as CS2 because it doesn't need all the different programs that CS2 needed. No, things like ImageReady were built into Photoshop CS3. That wasn't so bad until I noticed a week or so ago that the animation feature in CS3 had updated itself and changed completely. It gave me a certain period of time that I could utilize to animate it. Of course, I was making a blinking signature so it took many different layers, which made things confusing, before it was completely done. Before, I could just put a time down and it'd change according to how much time had passed.
Unfortunately, the program takes a while to start up. I suppose it takes up quite a bit of space if it is slow. Sometimes, it can cause your computer to lag, which can cause quite a problem. Though, if you're worrying about that, you can always get the Photoshop CS3 lite version which uses less space.
You can create beautiful images and graphics with CS3. It does the job and it does it well. I have been able to make avatars and signatures as well as graphics to catch the attention of my classmates during class. So I'm quite happy with the product.
Unlike CS2, CS3 looks more advanced and sleeker. It's not too box-like like CS2. They have similar features, but there is just a different look to it. With that look comes a different feel. If you're looking for something with appeal, you might want to try Photoshop CS3.