So I've had my iPhone 4 for for a little over a month and now it's time to sell my old 3G. Right now it isn't jailbroken or unlocked and is running 3.1.2 Is it possible to unlock 3.1.2 without upgrading to 4.0? I hear that iOS 4 on a 3G makes it very slow. What do you guys think will raise the phones value the most? Unlocked on 4.0 or leaving 3.1.2? Also, if i upgrade to 4.0, is there an easy way to downgrade?