I know it's not a apple product and doesn't have the ports ACD or TBD have, but it's glossy, LG IPS panel ( not quite as good as 21" iMac panel ). Fits perfectly on Mac mini and price until tomorrow is really hard to beat if you need a monitor. Just get miniDP to DVI cable.
I gave my new Dell P2415Q 4k after using it for a few days to my son, as I prefer these to 24" 4k because 21" is still better form factor for 1920x1080 ( my opinion ). These are very sharp, there's no antiglare coating and color reproduction is excellent. I would hope apple will make a 21" 4k standalone. I as like like my life, I will not hold my breath waiting So in the meantime these fill the gap until something better comes along.