I've been using my 24" iMac/1GB with Leopard for about a week now, and although the performance has been acceptable most of the time, running multiple applications such as those in CS2, can cause the system to absolutely crawl with 1GB of RAM installed. (spaces, stacks, app switching etc...are very noticeably impacted and are essentially useless features without sufficient RAM installed) This adversely impacted several meetings I've had with clients in my office, since the system would take forever to switch from one app to another; we were left sitting there for minutes at a time, twiddling our thumbs while the system was swapping. Installed 4GB of RAM this morning, then opened ID, PS, iTunes, Mail, Calendar, Safari, and Activity Monitor. The difference is amazing; Leopard functions flawlessly under a heavy load now! Well worth the $137.00 for the 4GB kit. http://www.macsales.com/ If you've been toying with the idea of upgrading the RAM on your iMac, just do it; 1GB ain't enough for Leopard.