What resolution are you guys playing at? Rather, what resolution does the client use by default?

The game will definitely choke on most Macs (even on Windows) if you try running it at the native Retina resolution of 2880x1800, so you'll want to make sure you're setting your client to use a resolution of ~1900x1200. My download isn't complete, so I can't test just yet :\

If there are no performance workarounds, Square Enix will be forced to issue refunds. There is a valid assumption by the community that the Mac client should suffer no more than ~20% performance penalty compared to Bootcamp Windows. If the performance hit is more than 20%, then SQEX has to admit that the client is next to useless.

They really should have spent the past 2 years creating an OpenGL rendering mode within their 3D engine instead of just wrapping it with WINE