The Maxwell cards show almost no gains over Kepler clock for clock with the web drivers. In some cases the 680 is winning. The benchmarks are so different to the performance that should be expected if you have seen the gains a Windows user gets with Maxwell over Kepler.
Nvidia said in their recent blog post that Maxwell beta support has been added for the first time.
End of the story unless you want to call Nvidia liars. You do so much for this community by helping people install their drivers. There's no point ruining that reputation with useless arguments. Life is so ****ing short and you really want to debate this ****ing crap?
Imagine 3 levels of GPU enablement:
1) A GPU just happens to be enabled by the NVIDIA web driver.
2) A GPU has beta support, as in, the company acknowledges that the GPU works with their drivers.
3) A GPU has official/full support as a Mac Edition product.
There are no official Mac Edition versions of any Maxwell card. NVIDIA's blog post suggests that the Maxwell GPUs have gone from (1) to (2). That is, for the first time ever, NVIDIA has publicly acknowledged that their web drivers enable the Maxwell GPUs, despite the fact there are no official Mac Edition products based on that GPU architecture. That is, they are (for the first time ever) officially acknowledging that they are enabling non-EFI cards to work with their web driver. "Support" has a lot of weight behind it -- does this mean they're going to start taking customer phone calls when people are having difficulties with their Maxwell cards under OS X? Back when these cards just silently worked, they sure weren't doing that.
The new drivers give significant performance improvements in very specific areas. The point I'm trying to communicate to you and everyone else is that these specific areas are in CPU-limited cases, based on my experience. There's a reason why Unigine Heaven on a GT 650M didn't get twice as fast, while other cases did get a massive improvement. There's a reason why higher-end GPUs got a larger speed boost than their lower-end cousins, as I mentioned earlier it's because those GPUs are usually completely CPU limited even at high resolution, ultra settings and max FSAA. This can easily be seen by running OpenGL Driver Monitor and enabling the "GPU Core Utilization" on any NVIDIA GPU, if it's less than 100% then the GPU is not being fully utilized.
My GTX 980 got a large improvement in World of Warcraft, but even at 2560x1600 with Ultra settings and FXAA, it's still barely pushing 75% utilization with the new drivers (up from 50% or lower with the older drivers). I see similar improvements with a GTX 680, i.e. both the overall framerate and the GPU utilization has gone up, but it's still not able to reach 100% utilization. This is a classic case of the game being CPU limited, and thus the large improvements to driver overhead found in the new drivers allow any CPU-limited case to perform much better with the newer drivers.
I believe that because the Maxwell GPUs aren't found in an official Apple or NVIDIA product, there is still plenty of GPU performance left on the table, even with the latest drivers. NVIDIA has obviously done work to make these GPUs function in OS X, but probably didn't spend as much time tuning the performance of the GPU under OS X as they did with something like GK107 or GK104, both of which are featured in official products. Personally, I hope that there will be more improvements coming, especially now that the driver overhead is so much lower than it used to be. My guess is that given the large amount of CPU overhead in the older drivers, there was less emphasis placed on the GPU performance of a high-end GPU like GM204 because it was CPU limited in the vast majority of cases. Or, in other words, why spend a huge amount of time making the GPU run fast if the CPU can't keep up with it? You could make the GPU infinitely fast and it wouldn't affect the benchmark scores in those cases, and this explains your point about no gains over older Kepler GPUs (i.e. they're both CPU limited, so the CPU is the determining factor in the overall performance, and if you use the same CPU in both cases you'll get the same score).
NVIDIA appears to have solved that problem. Now that their driver overhead is much lower, I'd guess/hope their focus will shift to the GPU-limited cases and we'll see continued improvements to their performance, particularly on the Maxwell GPUs. Fingers crossed, at least.
As I said before, this is just my opinion, based on years of experience with the NVIDIA drivers under OS X. Feel free to take it or leave it. I'd just prefer to avoid stating things as hard-and-fast facts when nobody on these forums can really know for sure, because aside from anything else, it creates confusion for newer folks.