The 3G version of the iPad is unlocked, so if your carrier supports micro-SIM, it should "just work". Wait... what? Steve Jobs dropped the micro-SIM comment so matter-of-factly during the iPad introduction that it took us a moment to process -- Micro-SIM, aka 3FF or 3rd generation SIM card. Yeah, don't have one of those, and neither does any iPhone. Awkward...!
PCMag's Sacha Seagan fills us in:
3FF SIMs were developed by the European Telecommunications Standards Institute to fit into devices too small for a regular SIM. Where a regular SIM measures 15 millimeters x 25 mm, a 3FF SIM card measures 12mm x 15mm.
Today's "regular" or mini-SIM is the 2FF, much smaller than the credit card-sized SIM that was generation one, and the 3FF is teensy-tinier still. Sure, no one in North America uses them yet, but T-Mobile is getting them, AT&T is obviously getting them since they're supporting the iPad with data plans, and we're guessing over the next 3-6 months, more carriers will get on board too. (Engadget is saying the pipeline is set for Orange and O2).
And the reason why Apple went with the Micro-SIM in the iPad? Could be they needed to save space in a device already twice the size of an iPhone. Could be it's just Apple being kill-the-floppy-drop-firewire-Apple. If that's the case, it's quite possible the 4th gen iPhone will get it next, and then what would Apple do with all that extra space?