I about to down grade my 4.3.3 to 4.2.1 due to battery drain issue. I try to restore 5 time and changed form Pwnagetool (mac oS) to windows Sn0nbreeze. everything seem to work fine at first but after I reboot the phone few times then there is the battery issue kicked on. Lost at least 25% of battery life after 6.5hrs of standby mode with wifi, bluetooth, location service, notification, ping all turn OFF. (My other Iphone4 with version 4.2.1 never have this problem). I even reset the network setting few times but there no luck. The only I cool thing for this 4.3.3 that have the Personal hotspot that I need to use it when I away from wifi. Question is if the 4.2.1 have personal hotspot option or how do I can get this option from ?
I believe the Hotspot option only came up with 4.3. That was the first iOS version on Verizon, and that's when the Hotspot feature was added (if my memory is correct).
If you were having errors or battery drain, the only solid advice I can give is that you download the 4.3.X update manually (do NOT use the iTunes auto-update feature - it always screws up). Then go into iTunes, select your device, then hold Shift and click the Restore button, then choose the iOS version you just downloaded.
I never charge overnite cuz afraid it may over charge and cause the fire. It did happen to someone already. I lost about 25% of battery life on standby mode for 8hrs (no calls, no emails notification or location service). My wife phone running 4.2.1, battery drains about 3%-4% after 8hrs standby mode.