GSM is the way to go IMO (T-mobile/AT&T). Your sim chip is plug n' play with virtually any GSM phone (makes replacing/switching hardware easier). Plus, it opens the doors to more (or easier) International use. If
you still need/want to stay with the blackberry platform, the GSM Bold 9700 is pretty slick. I've had AT&T for years with no probs at all. Plus they have affiliate business discounts for a lot of companies. Enter your work email here to see if you qualify:
AT&T Business Center Portal