Another driving force was cost of data service. With Cingular's sky-high prices ($55 for unlimited PDA data + SMS, $10 cheaper for a BB), I ended up going with a pay-as-you-go SMS plan to drop my per-month costs to $35 for data. Through T-Mobile, unlimited data + SMS only costs $30, and the network's just as good in Corvallis and Minneapolis.
I'm sort of looking into getting the BB unlocked, then using a small loophole to get out of my contract. Cingular's raising SMS prices from $0.10 to $0.15 per message (sent or received) on January 1, which constitutes a material change to the contract. I have 30 days from then to drop it.
If money were no object, I probably would've gone with the Cingular 8525, which the local store just got in a few days earlier and sold for $450.