For a certain kind of WoW player -- specifically, the kind that has addons out the wazoo -- the days after a new patch are always days of terror. Which part of my specially-customized setup doesn't work anymore? Where are my chat windows? Why can't I move? Dear God, how do I live?
While this addonpocalypse is somewhat less extensive than the one that destroyed virtually all addons last December, there's still a lot of stuff that's just not working. Wowinterface.com has a nice list of updated 2.1 addons, so if something's not working, you can always check and see if it's there. But not everything is fixed yet.
Personally, most of my AllDeuce UI is intact, but my Autobar and ag_UnitFrames have bitten the dust, and I'm getting a lot more errors. I can live without Autobar, but not having any unit frames is a little wearing, even though I have ArcHUD for the super-important stuff like health and energy. "Can you kick me out of the party because I can't leave?" "Can you open trade? I can't." "Who's the enemy targeting now?" Here's hoping that all the addons will be updated soon!
How many of your addons no longer work? How do you handle post-patch addon confusion?