So today Apple released 10.10.3 which will of course cause issues with the cards that Apple refuses to put in the drivers. Specifically:
GTX Titan Black
GTX Titan X
Most other Nvidia cards don't absolutely REQUIRE the Web Driver so they don't need to be concerned with this fix.
There will be an "Official" Nvidia release for this, but until then we can use the latest Beta. (linked on our drivers page)
I am still working on a "Best" method to run this but I was able to do this without having to remove a GTX970. I recommend downloading the 10.10.3 Combo update from Apple instead of using App Store.
Running 10.10.2 I basically I went into System/Library/Core Services and opened "SystemVersion.plist" and changed the "14C1514" to "14D". This let me run the Nvidia Beta driver installer. This is where it got tricky. I needed to switch the plist back to "14C1514" in order to run the Apple 10.10.3 update. I ended up having to "repair permissions" and reboot but there might be a way to avoid that. I got a Java error with "14D" in the System Version when trying to run 10.10.3 Combo. In any case, with a working EFI you can easily fix things, though running with just EFI and no drivers is a bit sluggish.
Will update with an official procedure when I finalize. Happy to get feedback from folks who have tried this method or the nv_disable method.