Don't upgrade to anything higher than 2.2.1. I'm still on 2.2.1 and it runs great. It's so perfectly smooth and quick, it's almost like having an iPhone 4 (without multitasking and copy and paste of course). Anyway... I'm happy for now. My iPhone 3G is starting to show it's age on the outside though... I've got a ton of cracks, scratches and general wear 'n' tear on the outside of it. Still makes and receives phone calls perfectly though. Just thought I'd let you know. If you think 3.1.3 is fast, you should downgrade to 2.2.1. It's night and day. Believe me.