The patch is live and (supposedly) the servers are up. That said, we're fully planning on raiding tonight. Here are some helpful tips.
Your UI may be completely ruined. Anything that messed with a combat log is screwed up, and I know of only Recount having a new version that works with it. That said, keep in mind that anything can happen with a patch, so you may need to disable mods just in case.
Download the patch as early as you can. Don't be trying to log in at the last possible second only to realize you need the patch. If you can, start the download
before you do whatever you normally do for dinner, etc before the raid starts.
Get in vent if you have questions. You'll find plenty of lurkers who can tell you what's been going on in case there are issues.
Good luck!
And no, I didn't make that banner. Galt did.