I was using CS2 when I upgraded to Snow Leopoard, and while it worked, it didn’t work great. It was unstable (InDesign crashed repeatedly), and anytime I tried to do anything in Photoshop that changed all the pixels in a large image (i.e. gaussian blur, despeckle, etc.), it took forever. If you don’t plan on upgrading to CS5 anytime soon, you might want to keep a separate partition with Tiger, just to run Adobe CS1/2/whatever.