When I first saw the recent demos of the upcoming OS X upgrade from Apple, Leopard, I thought the same thing. Much of it just seems to be Vista with a little bit more development, and I'm sure that we'll see much of the same in future Vista updates. The Apple stuff is good, but it's not so far advanced over Vista that it offers a compelling reason to switch.
Of course, the fact that a Mac can run Windows (including Vista) has changed things considerably. My next PC will be a Mac, but I'll likely run OS X only as a novelty.