Hey, everyone. Like most, I was debating whether or not to just upgrade to SL, or do an Erase and Install. I decided to try both and note my findings and post my steps below. Running a Unibody Macbook Pro. 2.93 GHz, 4GB Ram Short answer: The clean install is running a LOT smoother than the straight upgrade. The first thing I did, was run a full Time Machine backup on Leopard, just in case the worst happens. In my backups, I exclude all VMs and System Files. Once the backup was complete, I went ahead and ran the SL upgrade. The installation process was very smooth. Took about 48 minutes to complete. When the system finally booted up again, I noticed that many aspects of the OS were running a lot slower than they should have, and I was experiencing many of the 'bugs' you guys have noted. -Animations such as dock magnification, spaces, and expose were very '-'laggy'. -Using the 4 finger gestures returned weird results when repeated. (Swiped up, desktop shown. Swiped up again, animation down, then back up again) -Icons were all over the place. -Asian characters floating around the OS. I decided to give a clean install a shot. either install Leopard, then run the SL update, or an Erase and Install from the SL disk. But DO NOT restore your backup until SL is fully installed. Now, once SL is back up and running, head into your Migration Assistant and start your restore. This took about and hour and a half to complete. Once that was complete, I gave the system a reboot and checked things out. -System was running VERY smooth. No animation lag. Expose and Spaces were running like normal, even with many windows open. -4 finger gestures were acting like they should, and did in Leopard. Very smooth. -No more random Asian characters. -Overall a much more flawless OS. For all I know, some of you may be happy with your straight SL upgrade, but I've read many threads where people have been noting 'bugs' which I experienced as well, before the clean install. If you have the time, and patience, I definitely recommend running a backup, then an Erase and Install of Leopard/SL. Hope this helps.