I also have the iMac i7 and had 4gb of ram. The performance was a bit disappointing, especially when working with a lot of layered TIFFs that were 1-1.5gb in size in PS CS5. Lightroom was pretty sluggish too. I just added 8gb of ram for a total of 12gb and the machine is now starting to live up to the expectations I had for it. Just about everything is running much quicker than before and I can run LR, PS, InDesign, iTunes, surf the web, and have iChat open all at once and not feel any slow downs. This is all my personal perceptions and I don't do tests to figure these things out. I just know that there was sure a lot more spinning beach balls before I added ram.