I can't believe I said I was going to wait 4 or 5 days before upgrading my Ubuntu machine(s).
Of course, I went ahead and upgraded one of the machines today. You're not surprised, are you?
So far, everything seems fine, although I did run into this bug: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/548891
It seems very specific to having a Ubuntu guest under a VMWare host.
Happily, the workaround in the bug report worked fine.
And my other machines aren't VMWare guests so I don't anticipate having this problem with them.