I generally hear people call it something akin to Portland-lite. Similar demographics, white, very liberal, young (it is right next to Amherst after all); a lot of rich kids really. However, much like Portland there's a lot of homelessness.
My only real experience with Northampton was teaching students from there. Out of the 40ish schools I've taught it was the only one who asked for accommodations for transgender students, so that's something that stuck in my mind. Though, it was a middle school attached to Smith college, so there's that.