[Billy Goat]

I'm not sure I believe they ever completely improvised as surely some planning went into the paper 'track tape' things Rick famously used to have hanging everywhere? As much as I wish they changed things up over a tour like they did in 2007/8 I think we'd complain about the 'bigger' tracks that were rotated out of the setlist when we see them! I think the main problem is that they have so much great material and not enough time in each gig to play enough of it to keep us all happy
Having said all that, it does kinda suck that I know pretty much exactly what the setlist is going to be for every gig they play now!