Taking notice of this Feldman thread, I had my first listening experience with Feldman last night through Coptic Light (Tilson Thomas).
Amazing orchestral colours and harmonies throughout, and I liked the overall rhythm (not really rhythm, kind of hard to explain really...) which reminded me of breathing in and out very slowly, or waves coming in and out of shore - more or less the same every time, with only subtle variations. It's really quite strange and certainly like nothing I have ever heard before... I would probably describe it as 'atonal minimalism'. One of the things I did while listening was try to guess what would happen next, although this proved surprisingly difficult! Everything happens so gradually, that it is very hard to pinpoint exactly where one instrument stops playing and another starts. You are aware of it, but it is as though the music draws you in some other way and forces you not to concentrate on this. It really does seem to exist outside of time, and indeed seems to have no beginning or end. I was hardly aware of time passing while listening, and when it was over I realised that I had stayed so still that one of my arms was asleep!
So I look forward to listening to more Feldman in the future, although you do have to be in a certain mood for it. Sort of like Takemitsu; but to the absolute extreme. The musical material is so thin, almost pure tone colour, that it requires a certain mindset to enjoy. Probably something that works best when listened to in moderation.