I got a new 27" base 2.7 ghz i5 iMac a couple of months ago and it is very slow. Much slower than my previous 24" C2D 3.06ghz running Snow Leopard. It bogs down frequently and hangs up, especially when I am running Aperture. Opening programs takes forever and I have had far more problems with needing to reboot this machine to recover from a frozen state than my previous 2 years with the last iMac combined. The new machine wakes from sleep very slowly and is slower to boot and shutdown. I am guessing it is starved for RAM, so I have ordered 8 additional GB to bring me up to 12. I hope this resolves the problem, but I am disappointed so far. I don't know if the problem is related to Lion or not, because my prior iMac runs great on only 4GB. I've repaired permissions and it does nothing to speed things up. Any other advice?