Recently switched from Blackberry 9000 and Blackberry 9700 to iPhone 4S and iPhone 5 respectively. Both on Digicel postpaid.
At home I already had poor signal quality on the Blackberrys, but the phones were still usable. Since switching to the iPhones the call quality is unusable most of the time (can't hear the other party) and the data speed is also unusable (most apps timeout, even when the phones say 3G or E).
Mind you I live in the remote bush of Barbican/Liguanea so I should expect bad signal.
Also both phones are AT&T carrier unlocked (legitimate unlock by AT&T, not hacked or third party) and both are running latest iOS and carrier firmware. These phones also both worked flawlessly in the US last month.
Time for LIME?