I'm running 2.7. Am waiting a bit to upgrade to 2.8.1 given the few horror stories I've heard, but these do mostly seem due to rogue plugins and themes. My theme is fine as are most my plugins.
I do use the ancient Spam Karma 2 and wp-cache. They've given me no problems so far but maybe it's time to replace them with something modern anyway.
Suggestions welcome. What's are good spam and cache plugins for 2.8.1?