In the Feb '08 Modern Drummer cover article with Bonzo's son Jason, the present drummer for Led Zepp, Jason says R&R is the most challenging song for him to play correctly.
"MD: Are there any songs you find particularly challenging to play?
Jason: I think they're all challenging in a certain way. That said, the most challenging Led Zeppelin song for me to play correctly is Rock And Roll.
MD: I think everyone realized how deceiving that song was when the Led Zeppelin DVD came out, and we got to see exactly what your dad was playing.
Jason: Oh, yeah, because you can see his hands. The snare is going all the way through the whole song.
MD: That shuffle is hard to play with a relaxed feel.
Jason: Youre telling me! [laughs] I almost want to play it open-handed because I can do it a lot better with my right than I can with my left. .... You have to lead with the snare. Jimmy [Page] also taught it to me. He said it was inspired by a little Richard tune, "Keep A Knockin." It's one of those things that I don't care how confident I'll be, if we do that song live, when it comes, it will be the one where I'm thinking, "Don't mess it up!" Someone once said to me, "Isn't the ending of "Rock And Roll" the most difficult bit?" I said, "No, no, no," because that bit changed every night for dad, so you can get away with just going around the kit doing the triplets or whatever. But most of the time, playing his stuff correctly is the most hardest thing to do- it's the the subtleties you miss."
Anyway, a good article for those of you who can't get enough Bonzo related info. Joey