I'm thrilled there's so much focus on 4K now. I actually just picked myself up a Seiki 39" 4K TV that I'm using as my computer monitor and it's suuper cheap. $389 on amazon. It only does 30hz at 4k, but I am using a GTX 570 so am lucky to get 30fps at that resolution anyway. It does 120hz at 1080p, which is awesome. 30hz isn't ideal for gaming, but is still usable. I was able to play DayZ standalone with my buddies online yesterday and my card was pumping out over 30fps with some graphics tweaks and the game still looked very nice - it was a crazy experience. I did need to use Custom Resolution Utility to add the resolutions to the registry because they were not being detected by Windows 7 or my graphics card, but after that, it worked beautifully. I'm loving the extra desktop real estate. It's like 4x 1080p monitors lol, how could you NOT love that? I am a hardcore PC guy though, so all this tweaking is not for everyone. When they come down in price I'm definitely getting a 60hz or higher 4k panel and then will use this for a TV for my room, or have dual 4K displays LOOOL. Waiting for the Nvidia Maxwell 880's to come out and will pick one of those up for sure.
For those who say 1080p is enough, I say pish posh. Grab something cheap like the one I bought, or even spend a couple grand on one that'll do 60hz if you had deep pockets, and welcome to the good life!