It's certainly not 99% positive reviews, it's about 70/30 (which, for U2, is phenomenal), but even most of the positive agree that whether it was the conditions or otherwise, it wasn't the monster event they expected, but U2 delivered what they delivered very well.
And yes, Coldplay and Beyonce had a significant weather bump. 'U2 Day' and the other two could not be compared weather wise. Even I was in a foul mood all day leading into U2, and I had the once-in-a-lifetime dream Radiohead/U2 Live Double coming up that evening. It was just an awful wet, windy, miserable day. Coldplay and Beyonce had hot, beautiful, perfect days leading in, and the lift in mood all around the place was significant.
But... I do think Coldplay pitched it far better. Were the songs better? No. Were their theatrics over the top? Yes, but probably not to a lot of their audience (I mean, if you think Fix You is a great song, you probably think fireworks, lasers and butterfly confetti are awesome too.) Coldplay definitely played the crowd and mood better, but yes, they had a better crowd and mood to work with. They have played the festival four or five times now, so that they know exactly what they're doing might not be surprising. There is a bit of an individual art to it there, it would have been a change for Bono (less choreographed, far more spontaneous, and far, far more open), and the UK bands who are well practiced with it do always tend to nail it best.
Beyonce just put on a big show. No depth to it, obviously. It was like the opening number at an MTV Awards blown out over one and a half hours, on a much, much bigger scale. A lot of it was very, very, very impressive in that sense. And the Sunday night slots do have an atmosphere of their own. It's the end of the weekend, let's be less serious, go on, I'm drunk, put on a Beyonce track and let's dance.
Like I've been saying, U2 did not fail, they just didn't knock it out of the park. Expectations too high? U2 can't reach the heights of other 'legendary' Glastonbury sets? Maybe with only a few small changes they could have. But they didn't. And they didn't need to, but you look at the shift when not knocking out of the park - getting good reviews, some in the media and public actually daring to ask "Umm, should we re-think U2?", the shift in sales - and you can see a little bit of what could have been. There's a credibility gap with U2, and something like Slane is nice, but only U2 fans know about it. If they'd nailed Glastonbury as they did Slane, it would have been a great set-up for them. They would have known that too. That's why they did it. No Line tanked, remember? U2 don't do things randomly.