Re: the playability of high level 3.X
I think some genuine, valid criticisms can be levelled at
ease of play for high level 3E; I mean, it's not something which you can casually hop into and expect to work seamlessly. That said, I find it eminently
playable.
I think you need to put the work in, as a player or referee. By this, I mean rules literacy, adequate pre-session prep, intimacy with your own character'a abilities, and having methods of quick-referencing things like spells and feats to avoid hunting through books.
I think it does require a rather more flexible understanding of "balance," inasmuch as I see balance being a dynamic process rather than a static state. Or maybe aspirational - something worth striving for in the course of play. While I might not go as far as
@Yora asserting
unbelief in balance, I think that the various dimensions of balance/imbalance emerge through play and are particular to any individual game. The DM needs to be aware of where disparities are emerging, and adjust accordingly as the game progresses. This might be a rules modification, the placement of a magic item to benefit a particular character. etc. Or simply allowing a character to progress more quickly in order to "catch up" in terms of their effectiveness - this requires trust, ongoing dialogue with players, and a collective acknowledgment that this is a desirable state of affairs.