Upgrade went fine for me, with one exception. I'm having problems waking from sleep with 10.6.8. PC will go to sleep but not properly, with hard-drive/fans still going. Pressing mouse/keyboard then won't wake it up.
Just noticed this since upgrading to 10.6.8. Haven't heard of anyone else having this problem, so maybe it's something to do with my configuration. Did update from Software Update, then tried Combo Update to try and get sleep working. Sleep was working in 10.6.7 but occasionally got stuck when putting to sleep. Now it gets stuck every time I put the PC to sleep. I'm not using a sleepenabler.kext.