Just got the 3G iPad for my friend. So I try to see if it works with Hong Kong carrier but cutting normal Mini SIM card to micro SIM. The contact point of my SIM card is different from the AT&T micro SIM card that is a little bit larger. To cut it, I just follow the size of the micro SIM of the AT&T card. The size is to tight that I need to cut the cut such that three sides of the contact points reaches the edge of the card.

Insert the card and it works!!!

The outlook of both iPad Wifi and iPad 3G is almost the same in the front.

A little bit different at the back, that a back plastic on the top of the case that is for the antenna of 3G.

And a SIM tray at the side of the iPad.