I went to the show in Pittsburgh last night, some thoughts...
Heinz Field (where the Steelers play) holds about 65,000. I'd guess there were maybe 40,000 or so there. Basically, the floor was full, the lower bowl was full (except behind the stage where tickets weren't sold), but the upper deck was only seated in about 1/4 of the stadium, the sections directly viewing the stage. So, it definitely wasn't sold out or anything. From what I see, bigger markets are getting 2 shows (NYC, Chicago, etc...) so I guess there's a demand in bigger cities which is great.
Wolfmother was the opener, I not only missed their set, I didn't even see their gear on stage by the time I got through security and got to my seat. I literally have no clue if they even played, by the time I could see the stage, it was set for GnR.
GnR went on around 8:45 and played until 11:15ish. Really, really good show. Just a great rock show, it was loose when it needed to be with extended solos, jamming on intros or outros, but it was also tight when it needed to be in regards to arrangements, song transitions, etc...
The sound was okay, I was in the upper deck of a football stadium, so you can't really assume a pristine mix or anything like that. Axl sounded pretty good, shaky here and there, had a rough time transitioning his voice between different registers sometimes, but the grit and high stuff was there, he went for everything.
Slash, without question, stole the show. Unbelievable guitar player. I'll be the first to admit I'm a big Slash fan and I'll also be the first to admit he certainly is not the most technically-proficient guitarist, but man, he is jaw-dropping good to see live. Perfect example of a player that gets a certain sound simply from his hands.
Overall, great rock show, good stage production, pyro, fireworks, the whole nine yards. I'd highly recommend this tour to any and all fans of the band.