@Vaccano: I have the Nokia 920 that was handed out during Build, and haven't had any issues with it myself.
The biggest issue I had was when I got it set up for AT&T, I couldn't figure out how to turn on the cellular data connection (I could dial out, receive calls, or turn on WiFi and then everything would work). The fix being to select AT&T in the Settings/Cellular menu then selecting AT&T LTE2 in Settings/Access point menu. Really should have just read the paperwork they handed out detailing
I had the same issue where multimedia messages would not work etc.
So what did you exactly pick for ATT. I had 3 choices
AT&T 3G, AT&T LTE 1 and AT&T LTE 2 .. for MMS
then for cellular provider it has AUTO and then a dropdown with 3 AT&T texts .. which AT&T is it ? I just left auto.
On the phone side it has been working fine. I just had initial setups which I am not sure are right. Also AT&T does not recognize the phone so I cannot get full LTE turned on. (the IMEI number is invalid -- not a Nokia phone)