US iPad 3G and using more than one micro-sim
I'm planning on ordering a 3G iPad from the US. I travel very regularly and plan on having micro-sim cards for the countries I visit all the time i.e France, UK, Germany and others. Obviously it would be a lot cheaper to have separate sim cards for each country as opposed to roaming on a single subscription.
My question is whether any micro-sim will work in the US iPad 3G straight out of the box. I'll have absolutely no need for the AT&T sim.
This post is a little dated, but, as long as I'm here: I just got back from Canada, where I was able to do exactly this: I went into a Bell store in Vancouver and got a microSIM for my 3G iPad 2 ($5). We took my AT&T SIM out and put the Bell SIM in, and it worked exactly the way it should have: I went to "Cellular Data" in Settings and it let me sign up for a variety of month-to-month plans; I went for 5 GB of service for $35. The only thing I had to work around was that the sign-up form wouldn't accept "CA" as a Canadian province; I substituted "BC", and it was happy. The service worked great, and was much cheaper than AT&T's international data roaming plan.
I presume I could go back to Canada and re-use the SIM to purchase a new plan, but I'm not sure how long that would work -- do SIMs (and their phone numbers) used in this way time out after awhile?
To perhaps extend the discussion a bit: I'm going to be in France and the UK in July, and would like to do the same sort of thing, ideally getting one microSIM and service plan that would work in both countries. Orange provides service in France and the UK, but I'm not sure if a service plan bought in France would continue to work in the UK. Any advice?