I've got 1.5GB in my 1.67gh powerbook and it does fine with CS2. I'm sure it's not as fast as a G5, but I don't hesistate to open photoshop. I'm not sure how "heavy" a photoshop user I am, I'm usually just converting raw files and adjusting levels and cropping. Photoshop is really a mac applications, it makes full use of the altivec instruction set, and at least in the past always been quicker than much "faster" windows boxes.

Matthew