The iPhone 4s is a refinement on an already stellar phone. The only areas from improvement from my perspective are from a technology fanatics point of view.

The new antenna setup in the 4S has given me superior reception and call performance over any other phone I have had on AT&T previously. But I believe there are always areas for improvement in the clarity of the conversation even though in this case its more on the carriers end than the phone maker.

I find areas of the design that could be adjusted to maintain stronger visual continuity (notification center for example) but overall there are very few areas where the design doesn't feel very well thought out.

Overall the iPhone 4S is a stellar phone that continues to refine one of the best phone designs on the market.