Well, IDK, I think I have slight performance improvements.

An Artechnica article mentions improved support for 4K displays for those that use externals. Also it will be supported apparently for 60Hz 4K on the Macbook Pro 2013:

According to others who have installed the new beta, 10.9.3 also apparently enables 60Hz 4K output on the 2013 Retina MacBook Pros. The Intel and Nvidia GPUs that power these MacBooks were previously capable of 60Hz 4K output when running Windows, but were limited to lower refresh rates in OS X. Higher refresh rates make for a smoother, more pleasant viewing experience and are especially useful when editing movies, playing games, or in any other activities where response time is important. Those with older Macs likely won't see 60Hz 4K support even after installing the update—the 2013 Retina MacBook Pros and 2013 Mac Pro are the only systems that support the requisite DisplayPort 1.2 spec. iMacs, MacBook Airs, and the Mac Mini will need to wait for a Thunderbolt 2 upgrade before they can drive high-resolution displays at the higher refresh rate.

There's no word on when the final version of OS X 10.9.3 will be released. The first beta of OS X 10.9.2 was released in mid-December, and the final version didn't ship until two months later.

No idea how that will relate to ESO and whether the GPU will be able to support it implemented or not?

.. they wouldn't have build in the new "miracle" nVidia driver 337.50 anyway, which in turn would've brought only DX11 optimizations to the table.

Well, from reading around it seems they can also cause bugs and mixed reprots on performance which is to be expected with Beta drivers

The actual benchmarking(no ESO data given) shows that the real gains are not quite so magical though I expect it will vary from game to game.

Still, I can remain jealous that the PC Nvidia drivers remain about one year ahead of the Mac Updates version.

The real 'miracle' is a reality though, at least for the future in the moves now towards really reducing driver overheads and lower API access for games developers. it's not often you get Nvidia, Intel, and AMD all together to talk about such things, from GDC '14. There is a really nicely written article here which discusses it with less of the 'PR' spin

ExtremeTech - Who needs DirectX? AMD, Nvidia, and Intel team up to demo ultra-efficient OpenGL

The linked articles are also worth checking.