A feature that I wanted in previous firmware, was the ability to change your number in the phone’s contact list, most people would not need this as they either buy the phone with a contract or PAYG sim and keep that number.
But for those who changed their number or put in a different sim card your number wouldn’t in iTunes or the iPhone’s contact list, but if you go to Settings > Phone > My Number then you can now change the number if you’ve updated to the new firmware.
Sam's Blog 