I just thought I'd throw this out there and would love to find out if I really am a incredibly fortunate case or if there is a silent majority that actually upgraded smoothly. I updated to Lion on release day. I did not do a clean install. I installed Lion on my iMac and my MBP. Other than a few small, well-known bugs (that will get resolved), I have not had one issue. No slow downs, no wifi issues, no printing issues, no memory leaks, no crashes, no iTunes issues, no Time Machine issues, no WOL issues, no wake from sleep issues, and no third-party audio plug-in issues. I am a power user, but did nothing magical except to drop in to Terminal to unhide my Library folder.