Ermm well when I went, its really crowded if you go near the front, i got WELL pushed when i saw The Feeling cos most people were older than me, I'm small and I wanted to be right at the front lol!!!
But if you go nearer the back theres normally loads of space, we had to go there towards the end cos my mums friend was feeling a bit claustraphobic and it was fine, really cool breeze and no-one pushing.
And theres a balcony but not sure how ya get tickets for that....