Thought I would share this for those who (like me) downloaded the Mac App store version, saw the scary patch notes, and opted to wait for the patch to deploy before playing.
Given the App Store patch appears indefinitely delayed, and given encouragement from others, I gave the game a shot, and I'm pretty happy I did. First up - I made a conscious decision to pick a play through that would not use any of the new NPCs for the long-term party. This is because so much of the patch note refer to bugs with new characters in chapter 5. That said, I made the most of their content early in the game, before swapping them out for other NPCs, and there were no real issues other than with Dorn - who from my experience is still best ignored entirely for the moment (others may have had more luck).
The most annoying aspect of the play through is permanent paranoia about the save-game reset bug. As we know is due to a memory leak, my strategy was simple - save and reload every couple of maps, or every couple of hours, just to be safe. This took the edge off some of the fun, but otherwise I had a relatively trouble free run through to the end of the game - which I finally completed this morning. First time I ever completed SoA with a legitimate run, the only previous time being with a Paladin who exploited item-duping and the old drop-kit-on-import bug to hit BG2 with all 25 stats and a fistful of tomes for the NPCs, so I don't think that counts
So yes, I had fun. Yes, it was definitely worth the money to play BG2 natively on my Mac. And yes, the lack of patch took the edge of the game, but not enough to ruin it. I would recommend this game to others, unless you are planning cross-platform multi-player.