I've only been the once a couple of years ago. The setting is indeed stunning and it's very laid back. The main stage is in a lovely bowl, there's plenty of space and they have some decent ales on tap too. I have to say though that I prefer my festivals a little rougher around the edges. Green Man is much like Wychwood in that it is perhaps a little too family friendly for my tastes but that's not necessarily a criticism & it certainly has it's good points. I just hope it doesn't rain quite as much for you as it did when we were there.
Photos and mini review type thingy somewhere among this lot -
www.pbase.com/tort/festivals