I thought there was a patch floating around. My bad. I'm not sure how you'd go back to 2.1, either. I have feelers out on the subject, but nobody's replied yet.
I knew nothing of a FRG22 patch floating around for non-rooted users, but if there is one, I'd certainly love to have it.
I went ahead and did the manual update to FRG01b. Couple of reboots in the early going and a ton of lag with the launcher, plus a couple of force quits, but I've had it installed for about an hour now and I'd say it's been running wonderfully for the last half hour or so. Still a bit of lag on the home screens but overall a much faster browser. Installed the Flash beta and tried a couple of flash intensive sites, all worked beautifully and quickly. No complaints at all there.
I did notice, I'm experiencing the same heat problem others have mentioned in the back near the camera. I've got a case on mine and I can feel it even through that. I've taken the case off to give it a bit of breathing room.
Was that issue ever addressed or resolved? I checked my Facebook sync and everything seems to be normal, 3G notification icon isn't going crazy or anything, but there's definitely some heat back there.
No negative effects on the battery thus far. When I applied the update, I was at 70%, now after doing so, and using it heavily for the last hour, I'm only at 60%.