It's pretty good. A bit more restauranty level of quality than Five Guys, but the beef doesn't taste as good. Great fries and buns and everything else at least. Best burgers in Boston imo are Flat Patties in Harvard Sq and The Avenue in Allston. Both are aaawesome if you like the thin west coast/in n out style.
Also they're opening Shake Shack around here sometime in the next few months. If you haven't had that it's basically Five Guys but so much better, and I like 5g a lot.