I'm running 2560x1440 and it is blurry. Not crazy blurry but pretty bad, that's on a pair of Dell 4k 24" monitors. Of course, I can only have one working at a time, aka the airplay mirroring "fix".
So all this did for me was allow for higher, although blurry resolution.
Maybe by 2019 we can use our HumanScale arms....