I've swapped monitor to an LG 34UM95, a 34" 21:9 monitor with 3440x1440 resolution.
It works great in 10.10 (at DP6 currently), but it has a weird sync issue. Whenever the monitor loses sync - like powering off the monitor, leaving it until display sleep sets in, unplugging/replugging it and such, the video signal is lost. Whenever that happens, the computer works 100% but the monitor can't get a signal, and the only way to get it back is to reboot.
Anyone know what causes this? Might be a driver issue för my GPU (ASUS 290X), but I'm leaning towards some EDID issue. Would extracting EDID and setting a CustomEDID tag in clover sort these things out?