Well Cs4 can suck it.XD Cs3 is better anyways and its more than 4 times less $. Mace, Cs stands for Creative suite lol
The most recent version (the only version they sell at this point) of standalone Photoshop is Photoshop CS4. It has a Manufacturer's Suggested Retail Price of 700$. Photoshop Elements 7 costs around 80$, but is not worth that much due to lack of functionality. To answer your original question, save your money and stick with GIMP, which has more features and is free. Besides, as Randle said, you are more familiar with it anyway.