The improvements are only marginal over the iPhone 4. Apple did was add a Higher MP camera and the A5 processor that is found in the iPad 2. A larger screen is what i really want to see on the next iPhone.
I do like that the new iPhone 4S is a hybrid GSM/CDMA world phone.
How can you say marginal when the GPU is 7X faster and the CPU is dual core? That alone will make the iPhone very snappy. Since the iOS and the users app can now run in two cpu as two independent threads.