xfly, I have had the same problem since I bought the new iPad back in March here in Sweden. I have exchanged it twice via Apple support and got a new one each time but the problem persists. I have tried the following:
- Tried iOS 5.1, 5.1.1 and 6.0
- Reinstall via iTunes and set up as new
- Reset network settings
- Exchanged the SIM card to one with another batch number/version
- Switched to my work SIM with totally different set of services on it
- Used a SIM/subscription from another operator
- Tried different APNs (while troubleshooting with my operator)
- Tried on several different locations, both roaming and local
- My operator confirmed that when one of these drop-outs happened, when the network tried to contact the iPad it did not respond. A while later, the iPad responded from another cell. No correct handover had been made.
The problem does not arise when having only Edge (2G) coverage.
To me it seems that the problem is the 3G handovers. No new iPad will fix that as long as they use the same cellular chip. Hopefully (for Apple) it can be fixed with a modem firmware upgrade since I will be returning mine over and over again until it works.