Oh I wouldn't buy any of it. Definitely not, but I enjoyed seeing them live although I haven't finished watching yet. They just generate that unmistakable feeling of being at a proper event (like we did at home to Leeds last season). Because of work I had to watch that on the telly as well, but you know what I mean. Obviously we've all got different tastes. Some will have even enjoyed Katy Perry! Another highlight for me was the guy singing Space Oddity in a bubble
I think some bands just sound better in open air gigs, like the Foo's at Glasto, whereas others can sound a bit flat outdoors but can rock an indoor venue. One of my favourite bands are The Courteeners, absolutely fantastic in an arena, but come across as a bit tinny at festivals. Exception being Green Day who would probably still sound brilliant if they performed under water.
The little kids on their Dads shoulders loved Katy Perry. As a bonus they'd av seen loads of other performers. Introducing them to live music at an early age can only enhance their future.