I can't successfully drive my Dell UP3214Q (3840x2160) and two Dell U3011 (2560x1600) monitors using the three Displayport plugs on my EVGA Superclocked GTX 980 (reference). I've also tried plugging one of the 30"s in via DVI.
Two monitors work just fine, but when all three are plugged in they're all recognized but I lose aero support in Windows 7, which introduces screen tear when I'm browsing the web, etc.
Has this issue been mentioned here and (hopefully) been addressed yet? For reference, I was able to run this exact configuration without issue in Windows 7 using 2xDVI/1xDisplayport on my old 7970.
EDIT: I tried plugging in an old 8500 GT to drive one of the monitors to see if that fixed it, but since that card is no longer supported by nvidia, I was unable to find drivers that worked for both the 8500 GT and my GTX 980.
So now my plan is to buy a $50 GT 720 just to plug one of my monitors in... but I'd much prefer to get everything running on my brand new $550 card instead since it has more than enough power to handle the load. Why offer three Displayport plugs if you can't use them all?