Unlike the iPhone, which usually is SIM-locked, iPad 2 3G model is carrier agnostic and is unlocked in United States. MuscleNerd has posted screenshot proof of iPad 2 3G running on a T-Mobile network.
Confirming iPad2 is carrier unlocked: http://is.gd/PAwtPX (same BB as iPhone…unlock status is in per-device “seczone”)The iPad2 unlock status was completely expected, just confirming it for those who want to use T-Mobile instead of AT&T. Doesn’t apply to i4
If you buy the UMTS/GSM model of iPad 2 (known in the US as the AT&T iPad 2), you can replace the iPad 2′s micro-SIM with one from another carrier of your choice like T-Mobile and can use it without having to worry about being locked to one specific carrier. However, Verizon model of iPad 2 is carrier-locked because its 3G chipset won’t work on a GSM network.