Default Anyone using the Z Ultimate on AT&T's LTE?

Just wondering if anyone's running the xperia Z ultimate on At&T's network, using the C6806 model? Any issue's or has it been smooth? I've been wanting a Z for a while. I finally feel like alot of the issue's are worked out, now that the 2nd gens are out. Also any Z1/s users here?

Cheers
Driv3r