After Verizon it seems like AT&T is throttling its speed to make LTE available in US. Today AT&T officially launched 4G LTE service in three new locations. Most of the areas which got LTE access are Albuquerque, New Mexico; Guaynabo, Puerto Rico; Reading, Penn.; and Salt Lake City, Utah.
Now AT&T covers LTE in 108 markets over the US. Hope soon it would add more areas to its network. Check out earlier expansions here.