I upgraded my external drive (via usb 2.0) to test it out, the very first issue was that I could not connect to my router it could not find it, I have the router with its ssid in non-bradcasting mode and under password protected, it could not find it and when it did find the signal it would get lost upon restart. I knew that under Tiger by deleting some of the plist files it would improve, so I deleted the entire prefs folder under the user account and under the system account, it did improve but it remain even better when I changed the location from automatic to "home" as for Tiger there where similar issues but everyone forgets because of the upgrades and hints etc, there where 3 upgrades within a short period after its initial release, alas Tiger on my main HD is very stable now but the lure of Leopard is too enticing not to try. A lot of folks have managed to improve their systems by doing a clean install, I decided to tough it out and stick with the upgrade to see how much I could fix: I fixed the wireless issue, the sleep issue and finally the system preferences issue (non-locking panes)I could not fix no matter how much I read so I did an 'archive and install' and it worked and I managed to keep my pictures and settings etc, I did hit the password issue snag upon restart but since I had a second account I logged in and reset my password from there, now im trying it out with no issues (for now)SO the plist files to delete are the following: systempreferences,network configuration, Directoryutility,Directory. I also know that the utility disc does not correct permission correctly so it prevents the system from flushing corrupt caches, try using cocktail and clean all caches, look at the Console logs to monitor if they are being cleaned or not, if not the manual way is also proper (finder>go to folders>/etc or /var>caches)