Ubuntu gotcha to be aware of: you probably DON'T want to do a Partial Upgrade

Unless you really, really, really know what you're doing (and I'm not a member of that group!), you probably don't ever want to say "yes" when Ubuntu asks you if you want to do a Partial Upgrade. One unfortunate reality is that it's a bit easy to fumble-finger your way into such a situation and then you get, as they so delicately put it, "a mixed Natty/Oneiric system of dubious functionality".