Saw em in 78. They were a great live show.
They were the second concert I ever went to (1981), the first I actually bought the tickets for. They constantly had girls coming up on stage to dance for about 15 seconds before security ushered them back off the stage. I didn't realize how unusual it was until I had seen many more concerts.
I always thought this video of "I Do" did a great job capturing the J Geils band concert experience. (I also liked the live version of the song much better than the studio version.)
"I Do" - J Geils Band