Any recommendation of a good 4K monitor? I was looking at the Asus PB287Q.
I actually bought one and plugged it in via DisplayPort daisychained from my Thunderbolt external drive enclosure. I took it back because I couldn't really appreciate an improvement in resolution from my 27" IPS 2560 x 1440 monitor — i.e., they were both inferior to the 5K Retinal display to about the same degree in HiDPI with screen elements sized to approximate those on the 5K. If there was any difference, it certainly wasn't worth the $600 for the Asus PB287Q, which is
not even an IPS display. YMMV depending on whether you value text resolution or graphic resolution more highly -- for me, text resolution was most important, and that's what my impressions are based on.
Perhaps when the 27" or 28" IPS 4K monitors become more affordable, I'll explore an upgrade. For now, though, the Asus is probably the best of the TN 4K monitors, and it's not appreciably better than a 2560 x 1440 IPS to my eye.