I'm almost never on EDGE so far as I noticed, in NYC it switched only once from 3G to EDGE, dropped the call then picked back up on 3G all within a minute.
The random restart has been a problem with BB for a while. The Bold is no different. It seems to happen for me when I'm using a BT headset to pick up a call. Just happened with the Bold last week and Motorola H15 (excellent headset by the way) and it takes even longer than the 8820 to reboot, seems like more than two minutes.