AT&T device user and I noticed the following on Galaxymod:
1) LTE fix must be applied to avoid band switching and dropout (3G, H+, LTE)
2) Google voice users will need to go to the website to reactivate phone as selecting within call settings causes carrier issues and LTE fix to reset
3) Location services for AT&T users (tower triangulation, no gps, no wifi) is non existant (Verizon based).
This is the first ROM that convienced me to root and apply for my S3.
Overall the ROM is amazing (FAST, lt pie, multiview, note2 cams), but because the developer doesn't have an AT&T device, there are definite usability issues for us.
I noticed similar multi carrier supported ROMs have issues with AT&T base devices (Synergy ROM).
I would love to see this ROM built on an AT&T BASE UCDLK3. I'll continue to use and report anymore issues for AT&T devices.