I second that. Sprint is spotty at best throughout Vermont and Western NH. Reentering the US from Québec, there's some LTE coverage a few miles away from the border down through Burlington, but past Burlington, I-89 is pretty Sprint LTE-less until you hit White River Junction. I-91 is no bueno, no LTE at all in Keene NH, I didn't hit any LTE signal until Fitzwilliam NH, where I picked up towers in Winchendon MA.
T-Mobile was better in the rural parts of VT and NH, but Sprint was better in the rural parts of MA. Go figure.