My own experience has been returning to the revamped "El Capitan Only" Mac client after tooling around in the Windows client for a while. On my own machine, an outdated custom-built "Mackintosh" with an 3.4 i7, 8 GB and a AMD 6870 card, the new client runs circles around the original release, which I honestly believed to be hopelessly broken. I have a very consistent 30-40 FPS with medium settings at 1080x1920, and even better performance in raids and dungeons. Client responsiveness seems as good as the Windows client. In short, Square-Enix fixed it. It's still a middleware port, and it's still less than it could be, but it is so exponentially improved from the initial release that I have to give credit where credit it due. I didn't think it was salvageable.