Sony tends not to push its flagship phones on US carriers, for whatever reason. Sometimes a tweaked version will happen along at a later date, and that was the case with the Xperia Z1. T-Mobile got the Xperia Z1s in January of this year, but it was still on Android 4.3. Well, not anymore—KitKat is rolling out now.
Sony announced the Xperia Z1s at CES earlier this month, and it quickly showed up on T-Mobile's website. So Americans looking to just own the handset have had a week to order one online from the carrier, while those wanting a deeper relationship with the device - to love it for what's on the inside, rather than the outside - have had to wait a little longer. But now their opportunity has come as well.
The new Xperia Z1s on T-Mobile is almost identical to the international Z1, except for the radio bands and some software tweaks. One thing that definitely isn't the same is the bootloader – it appears that T-Mobile has requested Sony not allow bootloader unlocks on this device. For a company trying to upend the traditional carrier model, this is awfully old-fashioned carrier behavior.