From what I have observed markhutchison is correct. If I am actively transferring data via the tethered connection the phone calls will go straight to voicemail. If I am idleing along, the calls will come through, but it will stall the data connection.

Unfortunately this is probably going to be a deal breaker with the BB. I love this thing, but I have to have simultaneous access, and the only reason I upgraded was to consolidate into one device instead of carrying the broadband card and a cell.