I can hear the pundits tapping furiously on MacBook keys already. The new iPhone is not a radical improvement. The iPhone 5 is more of the same. Apple missed the boat with the small changes in the iPhone. Those are valid observations but had Apple radically changed the iPhone it would have bordered on irresponsibility in this writer's opinion.
To recap, the primary change in the iPhone 5 over previous models is the screen size. At 4-inches the phone is taller than the iPhone 4S but Apple chose to keep the iPhone 5 the same width. The logic behind that choice is to keep the new iPhone as comfortable to hold in the hand, and that's a good thing. I have used a number of other smartphones with big screens and some of them border on the unusable due to being too wide to hold comfortably for very long even with my big hands. Width is an important criteria for comfort.
The iPhone 5 is faster, more powerful than previous models which is expected. It will be powered by iOS 6, itself an iterative upgrade on the iPhone OS.
While many will no doubt proclaim the iPhone 5 to be a miss due to the lack of radical change, I say look at it logically. The last time a product as successful as the iPhone got a radical change it was a total disaster. Remember New Coke?