What can people tell me on the max communication speed on using the BB as a tethered modem.

Anyone can tell me how it has worked for "Bell Service " in the US?

Verizon sets the modem speed at 115200bps. I can't speak for Bell South, either for modem speed or functionality, but if you look in network connections, select the modem and look at Properties/Configure the default speed will display.

For T-mobile it's 115k but sometimes I get it slower though. I think the average is more than 90k. I have to do another test on my connection to know for sure.

On AT&T, they upgrade their Edge for the iPhone and people have been saying they are getting at least 200k.

Wirelessly posted (BlackBerry8830/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/104)

If Bell roams on Sprint, then you'll get 400-700k avg. I even clocked over 1mb recently download speed on Sprint