I recently bought one of these cheap ($739 Australian dollars) next gen 4K monitors and wanted to post my experiences with it, with both OS X and Windows.
First, the basic specs. It is a 28" 3840x2160 display with a TN panel. The reason I say "next gen" is that it is one of the first 4K monitors to not use a tiled display. It has new controller hardware that can do 4K@60Hz over a single SST DisplayPort connection. So it appears to the OS as just a normal, single monitor, but with a really high res.
The main reason I bought it is for 4K gaming with my Windows PC which has 2 x Radeon R9 290x in Crossfire. In that sense the lower quality TN panel doesn't matter much, and the lack of tiled display should help with game compatibility (no Eyefinity needed). And indeed, so far I have tried Civilization V, Bioshock Infinite, Thief and Wolfenstein: The New Order (all the games I have installed) and they all worked fine at 4K@60Hz. Of course, if you put all the settings up to Ultra, don't expect the game engines to actuallly achieve 60Hz :)
But of course being a Mac fan I could help but try plugging it in to Mac as well. The Mac is mainly used for productivity work (lots of reading the screen) so a TN panel is not really acceptable, but heck why not try it out. My Mac is the original 2012 Retina Macbook Pro with discrete GPU (NVidia 650M 1GB). This laptop only has Thunderbolt 1 ports, which can only do 4K@30Hz, and indeed if I just plug it in that's what I get, and it works fine, but 30Hz is a bit too jerky and annoying.
But here's where it gets interesting. The monitor has multiple ports on the back, 2 x HDMI and 1 x Displayport. It also has a mode called PBP (Picture by Picture) where all the ports present themselves as 1920x2160 screens, and the monitor displays them 2 of them side by side on the one screen. 1920x2160 is small enough for Thunderbolt 1 and HDMI to both achieve 60Hz. So by connecting my laptop to the monitor using the HDMI port on the right, and one of the Thunderbolt 1 ports on the left (2 connections at once), each port drives half the screen and I basically get 4K@60Hz out of a 2012 rMBP.
Of course, the Mac still sees it as 2 monitors. But if you go in to Mission Control preferences and uncheck "Displays have Separate Spaces" the 2 screens are effectively merged in to one desktop and you can have windows bang in the middle of the screen, which is theory are half on one screen and half on another, but you wouldn't know it.
Some other points. You need to put the Dock on the left or right because if you put it on the bottom it will be off centre. Also the menu bar will only go halfway across the screen, and any apps you switch to full screen mode with also only fill half the screen. Also the HiDPI modes don't show up which is a bit of a shame, 1920 x 1080 HiDPI would be preferable to raw 4K. However if you can put up with these niggles and you want 4K@60Hz on a 2012 rMBP, it basically works. Though I personally have disconnected it because it was just an experiment. And if you're used to the quality of Apple displays you will not like the TN panel.
I'm sorry I can't give any info on how it works with a more modern Thunderbolt 2 Mac.