Got my T-Mo 6 that I ordered through Apple.
Popped in my AT&T SIM - all set and working fine.
I will say, this thing is a little big, and I really don't like the button on the side. I'm not sure I'll be as good with one-handed operation here. So far, I keep using two hands. I'm a little surprised that this is the small version. The Plus would be impossible for me.