Don't listen to all the people who say to jailbreak your phone. It is not great at all. If you want to customize youre springboard, you have to use a program called winterboard which is BRUTAL on the RAM. You're phone will become twice as slow as it was without it. There is a video recorder app called cycorder which is great for video but uploading to your computer is a nightmare (which basically renders it useless for typical users). iRealSMS & BiteSMS are both buggy as hell and slow on top of it (kinda ruins the beauty and speed of SMS). Other than that, there are no really useful apps for Jailbroken phones. PDA Net, which is by FAR the most useful app in Cydia installer, used to be free but not anymore.
I jailbroke by phone for 2 weeks and the phone slowed down DRAMATICALLY. Granted, it was significantly slower with winterboard installed, but even without it the phone did not have the same user experience. Anyone who says otherwise, is fooling themselves or is just oblivious to how fast the iPhone is with a fresh 2.2 install.