i updated to 4.1 from 4.0.1 keeping my old baseband (for no other reason than resale value.. dont need the unlock) with TU and started as a new phone (didnt restore from backup).
I was having battery issues (got through the day mostly.. just not as good as i was expecting) at 4.0.1(even with downgraded mobilesubstrate), but now it seems to be much better(newest version of mobilesubstrate). Usually make it through the day with 40+% left when i pass out at night.
I even installed lockscreen app and a weather plug-in expecting it to kill my battery (with updates on the hour) and it hasn't. Im really impressed.
as of now, it was a light day of usage(busy at work)..prob 25 texts, 30 mins of 3g surfin, 25 mins of phone calls, 10 mins of games (2hrs, 6 mins of usage)) and im still at 62%, and its 9:45pm. Took it off the charger at 8am.
In my opinion, it was totally worth the update there. HDR and gamecenter... whatever, cool to have, but battery life is win.
Im coming from 4-5 days of life on my old e-71x that died on me. It will always have a place in my heart :'(....