It's interesting, because most people are now praising the Vertigo tour no(even if they bashed it then), most have said SBS sounds the best it has in 10 years, and I've asked this before and I'll probably ask it again, when was the last time you saw U2 do something spontaneous?
I personally think...(notice...personally...) that the spontaneous nature of U2 was evident on the Vertigo tour...morseo than 360. You've got to remember, it's hard to be spontaneous when you have lights, visuals, and songs that move to timing and coordination of rock show. Basically you have to stay on track.
Remember the last leg of the North American Vertigo shows? Remember before the 2nd Encore there was a setlist switch? I always remember getting excited just after the 1st encore because the setlist would change....or someone might be pulled onstage to play....or something requiring audience participation. I liked that part of the show.....the part where U2 show that they're human and having a good time. Remember in Toronto when they pulled out Fast Cars? Holy crap? When they tried to call BB King? I love that shit. Remember in Detroit for the Zoo TV tour Bono ordered the pizzas? I was there for that too. Remember in Hamilton when Arun got up on stage and couldn't play? I laughed my ass off.....
The spontaneous moments do happen....maybe not as much this tour.
No...U2 aren't the band (like let's say the Grateful Dead) who can strum a few notes and then go into a rousing rendition of "Wire". They aren't that kinda band. It would have to be practiced....