Apple won't care for exclusivity... it just wants $$$ Whether $$$ comes from AT&T paying them off, or from another carrier.
I use AT&T here because it works (for me), and I don't have an iPhone. Work discounts don't hurt either. It would be either Sprint or AT&T (both give emp discounts to me). Sprint has fixed its network recently, but has only LG/Sanyo/Samsung devices, and no SIMs.
Not true. They have RIM Blackberry, HTC, Palm and Motorola devices also.