Updated two Hacks via the Apple store update, zero issues, everything 100% working as it should, BT, audio, video, handoff, Trim and anything else. My main mac hung while it was on the black screen with "8 minutes remaining" so I punched the reset button after about 20 minutes of zero disk activity. System restarted and went into the setup as if it were a new mac so I panicked a little. After I answered it's questions and declined iCloud upgrade it came up perfectly, even reopened webpages I had open before the update. So even though it got stuck for a bit it ended up working perfectly so I consider it 100% success.
Greatly relieved! Really nice to have two fully up to date machines.