Here’s a tip; save yourself some money and buy the WiFi version of the iPad instead of the 3G model (Thanks to my good friend Stephen McGibbon for the suggestion) and buy a Huawei E5 with the money you save. Not only will your iPad be covered for all networking eventualities but so will all your other WiFi enabled devices.
I bought one from my local 3 Network store in Linz as I have a data plan with them in Austria. The unit was sim-locked to the 3 Network when I picked it up but a quick download from DC-Unlocker and 15 Euros later I had the thing unlocked and working with all my sims.
I’ve been using the E5 for a couple of days and its an amazing piece of gear. You can use it as a standard 3G modem by tethering it to your PC or Mac. Or you can use it untethered, connecting to it over WiFi.
After experimenting with the various combinations I found that using it untethered worked best for me. I would also recommend skipping the client side software install. The device boots up with a 192.168.2.1 address so once the WiFi is turned on (Press and hold the ‘wifi/wps’ button above the power button until the blue ‘W’ indicator lights up) you can manage everything through the browser interface.
Don’t forget to change the default password and set your own (Strong) WPA key. You’re going to use this in public spaces so keeping the bad guys out is a good idea.