To add what others have said, UHD is fine without scaling. I've been using a 28" UHD monitor since last year on Windows 8.1 without scaling and everything is nice and readable and I mostly work with text (UNIX sysadmin and programmer). Those that say you have to use scaling on smaller 4K monitors for them to be usable have obviously never tried it.
ShaydeI've got a 32 inch bl3201pt and there's times I have trouble reading native stuff. Anything smaller than 30 inch would be very troublesome for me.