Let the hive mind of Engadget get that for you.
"I'm in the market for a new phone and money isn't a limitation. I'm also not partial to any particular US carrier, but here are some of the features I'd like to have: WiFi, GPS, good coverage in lots of places, push Gmail (a must!), physical keyboard (a must!), a touchscreen, decent battery life and a relatively slim body. And please, nothing that has a fruit logo on it. No offense to the fruit fans, though. Thanks!"
sorry, I missed that you were on Cingular (just saw mention of T-mobile) Well from my experience much of Cingular's network is 850 (not exactly half). In certain towns you really would be shooting yourself in the foot to loose 850. I don't know much more than that but you might ask someone at Cingular forums on Howardforums for the most acurate answer.