My wife and I have the small Samsung flip phones. We both love them. We were having signal trouble at home, but so was everyone else who came to visit, that is the problem really was a weak signal, not a particular type of phone or particular carrier. A new tower in the area just solved that problem (thank goodness).
The great thing about these Samsung phones is thier size. Tiny, tiny, tiny. They'll disappear into your pocket like nothing else. They're pretty durable, too. I'm usually pretty tough on phones and pagers and these have help up well, despite being dropped and banged around.