I upgraded to the 5 from the 4s.
Speed of the device and LTE network is very impressive. I am on AT&T and amazed at the difference versus their older 3G network. Get 18mb in my driveway download and usually see 5mb plus in LTE areas versus typical 500 to 1mb on a really good,day with 3G. Tat is a huge benefit if you have LTE available.
Battery life much better. Used to get a day out of a charge but typically was at 20 percent or lower end of the day. I now see battery at 50 to 60 percent available end of the day. Have yet to get into a low battery situation which is great.
Brighter screen is a big plus. Larger screen but consistent width and much lghter are all pluses.
The shift to new cables was a bit of a hassle but I love the ease of the new plug versus the older 30 pin connector. We got 9 years out of the old connector across iPods, phones, and pads. THe new connector will be short term pain for some due to expense and devoices that need adapters, but a longer term gain I think.
Bluetooth is better with low power mode and less battery drain. WiFi has better range than the 4s and seems to be less of a battery drain in my use.
Some have complained about the camera with purple haze on bright lights at night. I have not ticked it myself on the photos that I have taken. Low light shots for me seem to be a slight bit better.
Maps is better in terms of speed, offline caching, and turn by turn. Some definite gaps in points of interest but I find Google with gaps on occasion. Mapping is hard and will improve with tuning and cleanup. Much better resolution on zooming in on Apple maps for me. But I use turn by turn which was not an option with the old maps on iPhone. I have a shortcut to Google maps via web browser but have not used except when I needed public transit or street view. Which is not that often FOR ME.
I have seen fewer dropped calls than ever with this latest phone. and improved audio quality in general.
Siri is better with more options on movies, weather, sports, etc and the faster processor plus LTE makes it more responsive and useful to me. Part IOS part IPhone 5 benefits.
I don't like the new App Store as much as the old one in IOS6 because browsing a list of apps for calculators or whatever is ow one screen per app versus a listing. But updates don't require passwords, so there are some tradeoffs that I like.
Overall fit and finish is amazing. But Apple products need cases or they will get scratched and the same is true of the 5.
Overall, I think it is an awesome phone. Huge step up from a 3GS or 4 but still nice from the 4s if you can justify and use LTE.
Neil