I've been lurking on this board for ever, but I had to finally register to reply to this one!
"The Rolling Stones Rock and Roll Circus" is a strange beast. Some parts are almost totally unwatchable, and others are unmissable! The circus stuff is pointless and mildly irritating, but some of the music is terriffic. I am also a big Jethro Tull fan, but that performance is really only interesting to me because you get to see sixties Jethro Tull. I'm pretty sure it was entirely lip-synched, and Tony Iommi was even "playing" the slide guitar parts without a slide. Wierd, because all the other songs seemed live.
The real gem here is The Who performing "A Quick One, While He's Away." This performance is one of my all-time favorites. If I remember correctly, the movie was never released in the sixties because the Rolling Stones felt that The Who outperformed them. In my opinion, the Who blew the Stones out of the water.
Also interesting is "The Dirty Mac," which was basically John Lennon, Eric Clapton, and some other musicians playing Yer Blues. Not great, but interesting.
I'm pretty sure it's available on DVD and CD.
Now that I'm registered, I'll have to get around to sharing my guitars!