The iPhone 5 is fucking awesome. I won't go into the hyperbole about the "jewel-like" construction or whatever the hell they said, but it's well built, feels light but solid, and the three features I gave a shit about work great. That's the LTE, the speed of the phone in general, and the camera, which is amazing.
I really don't feel the need to carry a camera with me anymore, this really does replace the Canon. The only time I'd feel the need to actually carry a camera now is maybe for vacation due to the zoom lens. Otherwise, this is more than good enough.
If you're already on iOS, and don't already have the 4S, I'd say it's worthwhile. If you've already got a 4S, unless you REALLY need the LTE speed you probably don't need the upgrade.
They do look nice. I'm not much of a cellphone guy but this did sort of peak my interest. Only real downside I could find seems to be that if you are lost in an unfamiliar area you may be forced to eat the other members of your party to survive.