http://www.amazon.com/Seiki-Digital-SE39UY04-39-Inch-Ultra/d...
But it can only do 30Hz at 4K due to its limted inputs. You can game on it at 1080p@60Hz (hopefully without any scaling issues since 4K has exactly 4 pixels for every 1080p pixel).
You may notice a little bit of stuttering during long, slow pans, but for everything else, it should work pretty well.
I'd be interested to see this display in action (not quite interested enough to experiment with $500 though) to see how it affected my vision of things.
LCDs have a continuous backlight and the liquid crystals need to change orientation to change frame. There's no flicker as long as they're showing the same frame. Here the flicker is noticeable as jerky motion, and is mostly just a problem for video, games, mouse cursor motion, smooth scrolling, etc.
That said, the points above about the mechanics of LCD's being different enough that I might not object are reasonable. I've really not tried using a 30hz LCD display.
The obvious difference in the scenarios you mentioned is interactivity. I find something charming about the 24hz look of traditional film (often even lower in animation, where "animating on twos or threes" can drop the effective framerate down to 12 or even 8 FPS), but I sure as hell wouldn't want to use a computer at 24FPS. Even outside of games, 120hz feels significantly better than 60hz just moving a mouse cursor around on a desktop.
I'm holding onto the idea that it's something that has to be pointed out to you before you really care, but beforehand there is still an unconscious negative effect. Say, you're talking about the steps you took to eliminate a frame of lag from a game, and it seems ridiculous and pointless to a layman, but then they turn around and complain that their game feels "unresponsive" or "floaty" ("I pressed the button and he didn't do anything!") The problem still affected them, they just didn't know what to attribute it to (or perhaps having not experienced, say, a PC FPS played on a CRT monitor, they don't have a frame of reference for how responsive a game should feel).
The thing is, movies aren't shown at 24fps - they actually flash each frame on and off a few times to reduce flicker.
It used to be done with a multiple bladed shutter on film projectors, but I believe digital projectors and TVs can do the same thing (on the TV if you turn off that awful motion interpolation that they all have turned on by default for some reason).
But one thing movies don't typically have is a very fast moving mouse pointer on the screen all the time... The mouse, and fast scrolls on web pages and stuff will likely have issues at 30Hz.
If you look on eBay for QHD (2560x1440) monitors, the ones that include a Displayport input are about $100 more than the ones with only HDMI, because they can be used by so many more computers.