I never liked a lot of their stuff that made it to radio, but they could tear the roof off live with their more bluesy roots rock stuff. They had a Hell of a harp player whose name escapes me. That was a great live band.
I saw them a good nine or ten times and they were never less than excellent. I saw the Aerosmith make the mistake of letting the J.Geils Band open for them in the mid-70's. Big mistake. About half of Aerosmith's schtick was taken from the JGB and it was apparent. It could have been worse, it could have made it a three band bill with the New York Dolls in the middle that would have totally exposed where Aerosmith got their act.
RIP John Geils, it was a fun ride.