What is the difference between Photoshop CS4 and CS2?

I used CS2 in high school and I am very familiar with it. I wondered if anyone knows the main differences between the two. Is CS4 basically just a better version of CS2 or is it a totally different program?What is the difference between Photoshop CS4 and CS2?
Any new version of the program is an improved version of it.





For example, Photoshop CS2 does not work well with intel macs or windows vista, because they did not exist when the program was released.





There are several new tools in Photoshop CS4 from CS2: Smart Objects, Smart Filters, Quick Selection Tool, Zoomify, 3D capabilities and lots more, not to mention the improvements to camera raw and bridge.





If you are worried about not being able to figure out the program because it might look too different, I wouldn't worry, its not really that different, almost everything from cs2 is in the same place.What is the difference between Photoshop CS4 and CS2?
Both. It is a better version of CS2 and a totally different program.





All of the CS4 components integrate much better with each other than they did in CS2. Additionally, many tasks are much easier to do with CS4 than they were with CS2. The upgrade from CS2 to CS3 is just as big as the upgrade from CS3 to CS4. Which means you're looking at a significant upgrade.





From the totally different program aspect of things, all of the CS4 software has been designed to take advantage of dual/quad processors if you have them. CS4 is a memory hog and you don't want to use it for video unless you have at least 8MB of RAM and a 64-bit operating system.





All in all, it's a nice upgrade and I think you'll enjoy it.