Goggling led me to an article by Paul Landmaker, at the suite101 Web site, about his take of the genre. Here's an excerpt of his post:
At times, your eyes go shut and you smile as you wallow in the sounds. It's got a pleasantly anesthetic quality about it. [T]he music and its atmosphere is almost like an aural drug.
The vocalists sing like they're only singing to you. They're not trying to dress up their voices with gimmicks.... They seem to make their music for the sake of its beauty or artistic qualities. They're not out to please their audience, marketers nor anyone else, but themselves.
This is comfort music, but not the soft and cuddly sort.... In this sort of music lies real art -- ear candy, if you will. If you want to find the artists in a town, go down to the coffeehouses. If they're not there, you'll at least get really close to finding them.... It's not so much that it's where they play, but it's the artistic qualities associated with coffeehouses.
So the keywords are pleasantly anesthetic, real art, no gimmicks, and comfort. No wonder I'm liking it. More coffeehouse music please.