Apple's choice of a new format of SIM card for the iPad is one of its most cynical moves in a while.
While it is a standard (and apparently T-Mobile has mentioned it previously and it's indeed been around as a concept since 2003) it's conspicuous by its absence as a topic for discussion at the next big SIM conference in April.
It seems like it's being done to give Apple - and its operator partners - yet another control point. The easiest way to ensure an iPad-specific data tariff (and whatever deal has been done behind the scenes) is to have an iPad-specific SIM card. In theory the device might be "unlocked", but if you can only get microSIMs from specific operators on a handful of tariffs, you're still constrained.
I'm willing to wager that Apple and/or AT&T has made an interesting deal with microSIM suppliers - it wouldn't surprise me if they've bought up a sizeable fraction of the total manufacturing capacity for the next year or so. If it's been around since 2003 with no uptake, there's probably just a couple of dusty production machines sitting in the corner of a factory somewhere. Sure, I'm sure lots of companies will now be revamping their SIM portfolio and forecasts, but it should enable the early iPad operators to keep data pricing under strict control (and more importantly, sell new connections rather than let people re-cycle existing data SIMs) for 6-12 months I'd say.
Contempt for the customer, in my view.