Belatedly catching up with Steve Smith's eloquent recap of Pierre-Laurent Aimard's Zankel Hall concert, I was startled to find him treating Cage's 4' 33" as though it were an O. Henry story, susceptible to plot spoilers:
At its inception, 4' 33" was about challenging preconceived ideas of listening as mediated by the concert hall experience. That's a good trick, but it really only works once, after which reported accounts spoil the surprise.
With all respect, that's nonsense — as I, at least, discovered the first time I actually heard the piece performed, after years of merely knowing about it. Sure, 4' 33" is "about" rethinking the way we listen, but only in the same sense and to the same extent that Beethoven's Ninth is "about" rethinking the question of whether a symphony can have words in it. Before either piece has that kind of propositional content, it has auditory content.
4' 33" consists of a particular group of sounds, around which Cage placed the gilt frame of Art. Experiencing the piece means listening to those sounds, no less than in the case of the Sibelius Violin Concerto. It doesn't sound like Aimard was prepared to let anyone do that.
To suppose, as Steve and evidently Aimard do, that the ideas behind the piece exhaust its essence is like mistaking the act of putting an item on a to-do list (memo to self: listen attentively to ambient sounds) with actually, you know, doing it. I would never claim that 4' 33" repays as much repeated listening as Der Ring des Nibelungen — that's one of the things that makes the latter a greater work of art — but once would probably be a good start, spoiler or no.
Afterthought: I once heard the poet and memoirist Mary Karr talking in a radio interview about the importance of memorizing poetry. She said that a poem is the only kind of artwork that you can keep with you in all its dimensions, and that struck me as wise and true. Your memory of Le Sacre or The Potato Eaters or Moby-Dick will never be other than incomplete, but memorize Kubla Khan and you can carry it with you in its entirety. It occurs to me that 4' 33" — which you can arrange to have performed for you at any time you choose — may actually be in the same category.