Yeah as an arty twat it is a bit disappointing. For some reason though I usually find discussion about art (and often music) online often just lead to horrible wanky conversations what with it being so subjective and whatnot.
Anyway in a vague attempt to help this thread along, I'm currently loving James Turrell's stuff. The Rodan Crater project seems like one of the most amazing things ever and I wish he would finish it so I could go over there and be amazed. I fucking love his stuff but have only had the opportunity to see a couple of pieces in the flesh or lack thereof. The way he uses light and space is mind boggling.
I don't know if he would be classified as Post-modern. I don't think it matters, he's awesome.