For about a month now my NVidia experience has been buggy me to upgrade.  I gave in to upgrading my driver, and after a very short trail period I have revert back. 
 
I ran into a performance issue with driver 340.52 on ESO.
 
(For some background of my build I run 4 EVGA-Signature Titans the non-black addition in a x79 ASUS black motherboard with an Intel i7 4960X CPU all water-cooled everything GPUs, CPU, and chipset.  My water cooling solution is very extreme all GPUs even under 100% load never get above 11c of ambient room temp. ) 
 
I have been running driver 334.89 with 3 screens combined at 5760x1080 resolution with everything turned up to the max and getting full 60 FPS in ESO.  When I upgraded my driver to 340.52 two things happen that I found a little odd.   First my video memory used on my open desktop with nothing running went from 430mb with 334.89 to 695mb with 340.52 and in game GPU usage in game went from 80% on all four cards with 334.89 down to 50% on all four cards with 340.52.  ((Please assume I have all GPU settings correct and absolutely nothing is user overclock (only overclocking is EVGA Titan factory overclock)).  This dropped my FPS from 60 on 334.89 to 42+- on 340.52.  This was a little frustrating and I don’t see anybody else having a similar issue.  I reverted my driver back to 334.89 and I am back to perfect solid 60fps.  (I also uninstalled NVidia experience after reverting back to 334.89 to stop the nagging.)  I can’t be the only one having performance issues with 340.52

NVIDIA still didn't fix Unigine Valley white artifacts and black screen in Skydiver, and during black screen graphic card work on full speed.
Sometimes AMD had such problems, now every benchmark work normal with Radeon cards.
They should sit with Unigine developers and to update software on version 2.0 or to fix that with drivers. 
 

thinking its just a bf4 issue .Since the last driver ive had 4-6 complete game close events ,no error,no crash ..just all of a sudden game closes to desktop.Temps under 65C ,very low OC on CPU .4 -.8 .Not ever a BF4 issue like this(since game beta and all drivers WHQL /Beta)till this driver was installed.I dont believe any game update has happened since the driver release.  Im about to roll back too last Beta .

Oxymoot, I am sorry you are having issues with this 340.52 driver as well however I am also glad that I am not the only one.  Although I do believe are issue are different as I am not having any reliability issues with this driver.  On the 3d power setting I always keep mine set at the maximum power setting, with the use of a  high end water cooling solution there is no need to choose any other setting.  The problem with 340.52 is for some reason it is capping the GPU usage in the game ESO.  This actually might be good thing for most people as stability would increase if you were air cooling, overheating, or have old or undersized power supplies, but I am water-cooled and stability is not my issue.  Outside of gaming if I use all four of my GPUs for security penetration testing and at 100% load for 24 hours my GPU temps never exceed 11 degrees above ambient room temp.  To put that in perspective let’s say room temp is 22C then the max my cards will go to is 33C.  Power is also not my issue I use twin 1500 watt power supplies that connect into dual 30amp 220v circuits via dual L6-30 twist lock connections.  I split the power supplies between the motherboard and the first 2 GPUs on one supply and then on the 2^nd supply I have the 2 remaining GPUs and all the peripherals.  In my case with 340.52 I am not having any reliability related issues and no crashing of any kind however I did not have these kind of issues on any of the resent NVidia drivers that I have tried.  I am only seeing 340.52 cap on all 4 of my GPU usage in ESO not to exceed 50%.   This is why I had to revert my driver back to 334.89 and now I get 80%+- GPU usage in game.  I understand this is only one driver I just hope somebody from NVidia looks at these forums and sees this might be an issue and fixes it for future version.  I  would be very happy to provide diagnostic output if requested by NVidia.