Does anyone have a feeling how well Lion will run on a an iMac 2Ghz Core2duo 4Gb Ram? I know it's compatible, just don't want to do it if the speed will be crap. I can't install it on my main machine (iMac 2.66Ghz Core2duo 8Gb Ram) for a few months as I'm in the middle of projects that can't be disrupted. But my old iMac is available. Is it powerful enough? Or do I really need a newer iMac?