I upgraded from 4 to 5.
Other than a faulty home button, my 4 was still perfect but I wasn't prepared to get it fixed so I decided to just sell it and get as much money for it to put towards the 5.
To be honest, I don't really notice the difference, but that would be mainly down to the fact I don't have a LTE enabled tariff, the only provider of 4G in the UK at the moment is carrier EE, but I refuse to sign upto long length contracts anymore.
The 4 was a fantastic device though, but as a tech addict I wanted to stay ahead, and I figured owning the 4 for 2 years was long enough.
If the rumored 5S brings something worthwhile this year, I will sell my 5 for it. If the changes are minimal like how the 4S was to the 4 IMO, i'll skip it; and wait for the 6 or whatever they call it.
Basically, my concern right now is ios 7 and how compatible it will be with the iPhone 5