Speaking for myself, I work in the Tysons Herndon-Dulles area, and since NV, I have LTE everywhere I go.
Also, even in the suburbs, where I live, I am on LTE almost all of the time. There are only a few places were I drop back to really strong 3G, and only one very small pocket where I drop to 1x.
So, I think that the DC/VA/MD area is just fine.