I didn't get a chance to see Katy Perry live - really disappointed about that, however I did end up going to "The Lot" (aka the village?) and seeing the performers there was nothing short of amazing. I'd have to say, they all kicked ass, especially in 100 billion degree heat. Miley killed it, Cher Lloyd did a super fantastic job (she's the main reason why I went anyhow, even though she said she was living with a guy for two months, I totally disapproved of that), Pilots - speechless, and Avril Lavigne... wow, just wow.
The entire event was incredibly efficient - two stages, one prepped while the other was going live and vise versa.
About performers being exhausted, Vegas is brutal. It's so difficult not to party the very second you show up. I don't blame them.
Our itinerary was crazy, I was awake from 4am Friday to about 3:30am Sunday. No sleep, not even 5 minutes at all, I drove 7hrs each way. Can't wait for the next event!