Just got back from Leeds a couple of days ago. My first festival (aside from Evolution, but I live half an hour away and it's fairly mediocre), and just had a blast. Saw the following bands (in order).
3OH!3 - Not usually my thing at all, but good fun and the crowd were great.
Hadouken! - Absolutely amazing atmosphere. Crowd were so hot for them being hometown boys, and they busted out That Boy That Girl at the end (which I was ASSURED by two friends that they never play live anymore).
Kids In Glass Houses - Only knew a couple of songs, but stopped the tent from burning out after Hadouken!. Fairly good.
The Cribs - Disappointing. They probably would have been better if I had been nearer the stage, but watching from afar was boring.
Dizzee Rascal - Actually worse than when I saw him headline Evolution. The live band may be a cool touch, but I feel he works better with a DJ. Still fun though.
The Libertines - I'm a huge Libertines mark, so I loved this despite their lack of technical ability. Great singalongs and nostalgia.
Pendulum - Most violent crowd of the weekend. Had to be carried over the barrier to avoid crushing. Felt more like a rave than a festival act which isn't really my thing, but made up for it with insane atmosphere.
Local Natives - Didn't really get them at all. My quasi-hipster friend assured me they were incredible, but I just didn't get it.
All Time Low - I expected them to be awful live but they were actually okay. Too much unfunny banter between songs though; trying too hard to be Blink 182.
You Me At Six - Decent, but I suffered from not knowing any lyrics while the whole crowd sang along.
Limp Bizkit - Completely terrible and amazing at the same time.
Cypress Hill - Utter shite.
Weezer - Fantastic. Best non-headline performance of the festival, and best frontman. Rivers was all over the place, especially during the closer (Buddy Holly, of course) when he dodged a few security guards and made his away around the side of the crowd with about 1,000 festival goers in tow. No idea how he made it back to the stage but he did so. Hilariously ironic cover of Teenage Dirtbag too (as well as fun covers of Kids and Poker Face).
Paramore - Awful sound quality. Sounded like she was underwater. Disappointing, although I'm not a fan anyway.
Blink 182 - My favourite performance of the weekend. One of the first bands I ever got into at the age of about 11 (along with Green Day), and to be surrounded by similarly aged people belting out the lyrics to every song was amazing. I've head of sound problems, but I was too close to the stage to notice. Tom even managed to sing and play fairly well, and Travis was amazing as always. Between-song jokes were short but hilarious, too ("We'd like to thank the band Jedward for allowing us to cover their song")
A Day To Remember - Far too hardcore for me to listen to at home, but enjoyable in a festival context. Rowdy (if small) crowd.
Lostprophets - Biggest disappointment of the weekend. Sound quality was almost as bad as Paramore's, and even if it was perfect I suspect Ian and co. would have delivered a similarly mediocre performance.
Biffy Clyro - The band I most regretted not knowing more songs by. Very energetic performance, great frontman, and great crowd.
Queens Of The Stone Age - A very powerful performance, loud and driven. "No One Knows" tore the house down, even from where I was sitting (miles away).
Guns 'N Roses - Suitably epic with fireworks and a great light show (as well as the "wow they decided to show" factor). They didn't exactly end the festival with a bang, but it was a perfectly satisfying performance.