I bought this monitor new, and it certainly seems to have resolution/compatibility issues. I've had the same problems everyone else has mentioned using display port and HDMI. Different cables, computers, video cards, you name it.
I took it back to Microcenter where I got it for them to test. Same result. They took a second monitor out of stock and had the same issues. I seems to maybe work on a Mac, but nothing else. It either won't support the stated resolution, won't enter Windows when it tells you the resolution is wrong (even though it isn't), and does not get along well in a dual monitor situation either.
I have an older Dell ultrasharp monitor that I love and am trying to replace. The new monitor should not be so problematic that even a well-known sales/service center can't make it work. PLEASE look into this. I would love to be able to buy this monitor and use it!