BlackBerrys work well as simple phones, but you have to guard closely against data charges if you opt to go without a data plan. You get charged by the kb for data in that case, and it gets expensive mighty quick.
On Sprint, I'm paying $60/month (after simple discounts) for 450 minutes, unlimited messaging, and unlimited data. That's BlackBerry BIS data too, not some generic data plan that is worthless on a BB.
When I was with AT&T I was paying almost $100 for the same thing.
Like TXLady says, choosing the carrier for coverage in your area is #1. Then find a mobile they offer that fits your individual usage patterns. For non-BlackBerrys, her suggestion of Howard Forums is an excellent one.