I am on 3.1.2 and I hate it. I have been googling for hours and can't find a clear way to downgrade back to 2.2.1. I deleted iTunes 9 and reinstalled iTunes 8.0.2, downloaded PwnageTool 2.2.5 and the iPhone 2.2.1 OS and created a custom firmware. Trouble is the stupid Native MMS 2G package in Cydia put my iPhone on a reboot loop. iTunes won't let the restore process happen, so I'm going to restore to 3.1.2 again and THEN try to restore to 2.2.1. Pray for me.