Everything seems sharper.
I would vote most definitely yes, unless the price is just too much for you. But 4K can be had at a decent price. One question might be, how small is so small it is not needed, or the inverse - how large can a monitor be before 4k is really needed?
For me, the monitor size question happened around 24 inches. 2k or 4k there seems ok, but for larger, I want higher resolution.
Then again, I have a 15 inch laptop with (almost) 4k screen (actual 3.5k), and I love the screen. Part of the reason I love it is that is also an OLED screen, which gives greater dynamic range.
Aside from the monitor question, you also need to have a look at the ports on your current video card to see if it will support one (or two) 4k monitors. When I first moved up to 4k, I was disappointingly surprised to find out that my GPU wouldn't drive even one, much less two. And I didn't have the right ports on the GPU to connect either! DVI port? No. HDMI port - maybe. (Need to look very closely there, and the cable matters two).
I ended up getting a new GPU with two DisplayPort connections, and two DP cables to connect my monitors. Significant added expense.