Re: The National. I was a sorta fan, but was totally blown away by their Glasto performances (largely due to the fact I wasn't totally familiar with their material, so just enjoyed it as a casual listener)
For my dad, who was there only waiting for Foo Fighters and on my recommendation that I'd heard they were a great live band, was totally transformed by the show (and, oddly, was almost brought to tears by 'I Need My Girl'). The National are now one of his favourite bands, we've seen them again together, and that Glasto set will now always have a special place in my heart.
Different strokes for different folks I guess, but I can attest to the fact that it seemed to have gone down a hell of a lot better to non-fans.