First and foremost for me: reliable calls, anywhere and everywhere.
I just dropped my T-Mobile cell service because my employer gave me a Nextel phone for on-call purposes. The walkie-talkie thing comes in handy for data center and network support. Anyway, I have to say that Nextel has the worst cellular coverage/reliability I have ever encountered, and I have used a cell phone for 10 years (Sprint, AT&T, Voicestream). I'm constantly losing calls in places the T-Mobile service (and the Voicestream service before that) was rock solid. Ironically, the walkie-talkie part works everywhere, even when the cellular service won't.
I'll take reliability and stability over whiz-bang features any day. Then again, I'm an enigma.
JT$