I'm considering upgrading my iPhone 4 to a 4S. I love my iPhone 4, but it's beginning to show it's age. I'm finding the UI is becoming a bit laggy. Nothing too bad, but it makes it hard to do things quickly. I can get a 64GB iPhone 4S for $400, and probably get around $175-$200 for my 32GB iPhone 4. So it'll cost me $200-$225 net to move up to the 4S. Is it worth it? I'm not interested much in the iPhone 5 because I'd have to pay the full amount for it (prepaid). So the 4S is a good step in-between.