..."why are people asking how to downgrade on an Apple.com forum? It's forbidden here, Apple doesn't support it. Apple doesn't even allow it because you have to use a third party tool."
Very simple: Because Apple NEEDS TO START SUPPORTING IT! My 3G is slow and won't even run several of my apps without quickly crashing. I'll bet the problem is the 3G's paltry 128 mb of RAM (compared to 256 and 512 for the 3GS and 4, respectively). Apple should have given us a warning; I never would have upgraded. Apple needs to start supporting rollback to 3.1.3. I'm willing to go the third-party route, but the last backup I have (pre-iOS 4) is almost 8 months old, and apparently you can't restore any settings, text msgs, etc., from a iOS 4 backup to a 3.1.3 installation.