Is anyone able to change the resolution of the monitor to any other 16/9 resolution, other than 3840x2160? All the other resolutions are weird aspect ratios. I'm using the latest drivers 337.88, and am using the monitor over DP @ 60Hz. It's strange becuase when I use the HDMI I can use 1920x1080 and other 16/9 resolutions but not over DP.
You're not alone with this issue... I mentioned this back in December (http://en.community.dell.com/support-forums/peripherals/f/3529/t/19536444.aspx?pi23185=2) - but the half picture / sleep issue has prevented me from really using the screen so far.
I suspect it is another limitation of the scaler that can drive only two tiles instead of the full display.Whether or not these two scalers could be reprogrammed to also support lower resolutions remains to be seen.
You can switch your screen back to DisplayPort 1.1 mode (limits the display to 30Hz at full resolution but gives you 1920x1020 at 60Hz... unfortunately no 2560x1440 at 60Hz in any configuration works), but that seems your only shot at the moment.