I have accumulated a large number of their LPs over the years, and while I don't consider myself a huge fan, when I'm in the mood nothing beats them. They have a very European sensibility to my ears. I especially like the titles that MG refers to as "fanciful," including "Odds Against Tomorrow," "Third Stream," and "No Sun in Venice."
I have found over the decades that they were sort of a gateway jazz act for many people, along with Brubeck, Oscar Peterson, and Miles. I have seen large collections with very little jazz except for a couple of MJQ albums.