I used the iPhone 5 for a few days before giving it up to someone moving up from the 4, and after going back to the 4S, I had to take the case off because I couldn't get over how heavy/dense it felt compared to the 5.
Plus in addition to being lighter and thinner, the 5 is much, much faster, has a larger screen, has LTE, has better battery life. Sounds like it's better in almost every way a phone can be better...
Granted, iOS needs some work and everyone is "begging" for an OS overhaul, but this is what happens when you have a user base that largely consists of middle-aged people who could care less about technology. They just want it to work.
The fact that my mom can go from iOS 4 to 5 to 6 to the iPad back to the iPhone without changing her usage habits too much between devices and OS while adding features is a testament to the work they have done in this regard.