With the release of Mountain Lion 10.8.1, it was time for me to upgrade my Macs this weekend. If you have more than one Mac, check out this 9to5 Mac story on how to make a boot thumbdrive. It looks like the new OS image is larger than a single DVD so you need at least an 8BG flash drive, (a 16gb for me).
So far so good. I've updgraded 3 machines with no issues. My old MacBook Pro 13inch took forever to update, but it eventually finished.
You can find the list of Mountain Lion features here. A lot more dessert than meat and potatoes if you ask me. I'm still trying to make iCloud do something useful without much luck.