Took the plunge last night from 2.1.04 - I was probably the only one in the world still on this firmware - and did a full system reset/usb transfer. No problems at all upgrading my 101 to the new firmware. Here are my observations:
1) The device is definitely much zippier and apps run much more smoothly. I really notice this on Thumbkeyboard which before the update often failed to register about 20% of keystrokes when typing quickly.
2) The new Youtube app works well but is a bit slow to load the videos. Seems to buffer more than the market Youtube app.
3) The screen rotation is definitely a bit slower but not really an issue (mine is nowhere near the 10 second delay reported by others).
4) I do not have (and have never had) any of the wifi connection, sleep issues that others have seen. In fact device connects to wifi MUCH more quickly than before.
5) I did get one fc when I was reinstalling a bunch of apps after the update but I probably pushed things too far. In normal use I have not had any fc's.
6) Just an unverified observation but battery life seems about the same as 2.1.04. I have noticed before that after a firmware update it often takes a couple of charge/drain cycles for the battery life to normalize.
7) Flash on the browser (I use Dolphin HD) works the same as it did before.
My biggest disappointment is that the system reset changed my swap to 64mb from 32mb. In prior firmwares only an android (vs. system) reset would increase the swap. Too bad as I would have much preferred this space for apps.