I can't speak on Photoshop, but I have been using Flash CS4 for the past couple of days, and the performance is about twice as fast as CS3 (at least on my machine). That makes me smile because CS3 was so slow I would be pulling my hair out anytime I opened or moved a section (like the Functions panel or Library) of the interface and it would take 15 - 30 seconds to render. Maddening. So far CS4 is tits. I haven't even used any of the new features yet.