i got my iPhone 5 yesterday and so far have only played around with it a little bit. after all, it's basically just a taller and thinner iPhone 4 (that's the one i upgraded from), and not really a radically new design.
so far, though, i have to say that even though the form factor hasn't changed a lot, it makes a bigger difference than i would have thought. the new model is noticably thinner when you hold it, and the taller screen makes many of the list-based apps (and most of the apps i use are essentially list-based) quite a bit nicer to use.
what i mostly like are the small improvements: it's definitely faster than the iPhone 4, the speaker is better, the headphone jack at the bottom makes more sense, the camera is definitely quite a bit nice (in particular in low light), and by making it just taller, it's not as awkward to hold in one hand as the larger competitors.
iOS6, which comes preinstalled on the phone, is sort of ok. as everybody knows by now, the maps are really bad (even though i like to stress that the maps app itself is actually pretty slick, if only it would connect to quality data sources), and most other updates are pretty minor (if only it would be possible to hide this
VIP mail thing that apple decided everybody has to deal with now). i still have to start using siri, but so far i just don't have the desire to actually talk to my phone. i am not sure that i like the fact that we now have twitter and facebook being hardcoded into the OS, it's just not something that should be at that level of the ecosystem.
as a little side-note to the maps disaster: since i am interested in location-based services and all kinds of location concepts and apps in general, the biggest problem with the maps disaster hasn't been the maps app. i can happily ignore that and use google maps as a web app, and eventually google will probably release a native app. the biggest problem is that all my map-based apps now who the hideously ugly and often wrong apple maps, because as a native iOS app, you're using the MapKit API, and that means that every single native app now uses apple's maps, and not google's anymore. this is a huge loss for all the apps relying on quality maps, and while apple has promised to improve their maps, it will take at least months and probably even years to get to level of consistent quality, accuracy, and coverage that google has developed over the years. so don't expect those apps to look as pretty or be as useful as they used to be anytime soon...
so generally speaking, the upgrade has been as expected: a little nicer iPhone, a largely uneventful iOS update (apart from the royal maps screw-up), and other than that, life goes on as usual.