4G (since they are calling it that) is the gray area. Hopefully AT&T will start to actually push the speeds they claim they are capable of. Atrix users (don't crucify me) are complaining, by the hundreds, that the iPhone is DESTROYING the Atrix on speed tests. If true, AT&T has a problem, or they are simply misleading users and charging for it. All of the T-Mobile devices I've tried (G2, mT4G, Nexus S) are incredibly fast when it comes to data (provided I have some sort of a signal of course). The G2 and mT4G are obviously faster. I have yet to test an LTE device, but the Thunderbolt should be sitting on my desk when I get back from CTIA on the 28th. I'll post more then. But, even with LTE starting to "roll out", (IMO) if AT&T can actually begin to provide customers with the 4G service they supposedly have in place AND integrate that with T-Mobile's existing 4G network...Verizon should be VERY concerned.
Considering that T-Mobile were the first U.S. carrier to launch an Android device, and that has been their niche, as an Android user (hey, I love all devices) I'd be concerned about what AT&T is going to "lock-down". They already block the side-loading of applications, and honestly didn't seem to care about Android until they lost the exclusivity of the iPhone.