We have had some good ones at the GOAT in Portsmouth. Last time at the Manchester one I was not impressed, but it could be an isolated case being it was 4pm and we were probably their first one off the grill of the day. They had just opened.
Hop and Grind in Durham, NH is supposed to be a hot spot. Although 10 minutes away, we have never made it over to try it. The chef is well known and has won many accolades. He was just featured at a food show in Miami recently, put on by Guy Fieri.
https://www.hopandgrind.com/team