I drove all the way from Boston, MA to Easton, PA and encountered only a few 3G areas along the way. They were mostly areas with just poor service in general. There was only one area I found in Connecticut where I had a strong 3G signal with no LTE. In Easton with 2xCA from a mini macro pulling about 30Mbps in the middle of the day. When I was in Bethlehem, PA visiting my friend's family, I had 3xCA from a Sprint 8T8R site and I was getting up to 74Mbps.
Since getting my magic box setup, I've seen steady improvement in signal strength and download speed over the past couple weeks. No issues with any of our devices connecting to it. It's quite remarkable to go from barely any service to what is attached in the link above.