If you do any kind of productivity work, yes - gaming with a 1080Ti or better is just a bonus ;)
As for gaming specifically, an added bonus of a decent 4K display is that you can turn down/off AA settings - they compensate for jaggies due to lack of rendering resolution, of which you have plenty at 4K :)
The increase in real estate makes a huge difference (e.g. programming using an IDE, like Visual Studio), and the fonts look way better in 4K, so much easier on your eyes.
However, I am using a 32'' prosumer monitor (Asus PA329Q) and consider that a good compromise for size and resolution vs scaling (150% recommended at this size); smaller screens may have issues for you.
At this resolution it's also worth investing into a higher-end model, that supports features you find important, e.g. colour spaces supported, inputs, scaler quality, refresh range, freesync, gsync, variable refresh rate, HDMI standards (4K @ 60Hz requires HDMI 2.0 at 18Gbps) supported, HDCP version supported (HDCP 2.2 required for 4K video!), DP version, PIP etc.
For example I find displaying 50Hz pictures (for emulators supporting PAL systems) as well as colour space very important, and that limited my choices instantly to monitors recommended for photo/video production.
Then I wanted to watch 4K video from time to time, for that you need HDCP2.2 support - otherwise the video playback reverts to a lower resolution. That again limits your choices further, as many monitors do not support HDCP2.2 at all, therefore for example can't be used with FireTV or consoles for 4K video output.
You should make a list of exactly what you want from your monitor, and using that you can create a shortlist. Then if you have a chance try the selected monitors first in real life if not possible make sure the shop you buy from has a good return policy.
A monitor will likely stay with you for longer than any other part of your computing setup, so don't save money on it, unless you really have to.
Also check the monitor for screen defects once you installed it, use it for a few days for extended periods and re-check.
If you are using Windows, there is no hope of any kind of productivty unless you use Windows 10 - the last 2 updates finally support decent scaling etc., so you won't be looking at a blurry mess.
Your monitor will not display 4K @ 60Hz via HDMI (ie streaming devices, consoles, or even your PC, although for that use DP) unless you use high-speed HMDI cables, so make sure you have and use the necessary high-speed cable(s).
HDCP2.2 is also a requirement for this use.
Finally, if you care about that at all, at 4K you might as well get a HDR capable monitor, but it will take a year or two until decent models with the required brightness appear, rather than the simple 10bit 350 nit panels branded as HDR right now...
Post edited February 13, 2018 by IFW