It worked fine with Firefox 2.0, and I liked the clever way in which it did spell checking (although, of course, Firefox's spell checking works everywhere). People with lesser browsers will like it.
But despite the fact that the preview screenshots included a clearly visible Junk mail folder, the "finished" product has no anti-spam features whatsoever.
Cosmetic value and some decent, standards-compliant Web 2.0-like UIs are nice, but they will only get Apple so far. Having just renewed, I still hope that they will deliver a meatier, "real" .Mac upgrade this year.
Oh, and by the way, taoofunix.com is mine. Call it a hedge bet, if you will.