My feeling (like Josh's and Per's) is that the Mac driver should be what you get by default, in most cases, without taking any special steps.
If the concern is what you get when you're ssh'd into a remote system, then it's probably possible for the Mac driver to detect when it doesn't have GUI console access and fail. Then, Wine could fall back to X11.
We can't rely on DISPLAY being unset. It's set by default. That's true on Snow Leopard and Lion. I believe it's also true on stock Mountain Lion (whether or not XQuartz has been installed).
(The question of when to make this switch so that the Mac driver is the default is separate. OpenGL is my next major patch set. I hoped to submit it yesterday, but got tripped up by some changes in Wine since the CrossOver 12 base.)
-Ken