They are wonderful! When I was just a kid, my grandmother use to take me to see them on a regular basis. We'd sit in the balcony and listen to all the beautiful music. Arthur Fiedler was the conductor way back then and he was a performance in himself.
I also saw John Williams conduct on several occasions. The current condutor, Keith Lockhart, is my least favorite. A bit too oh so politically correct for my taste. Still the music remains and the Pops really know how to deliver it!