I just got one of these as well. After a few hr of testing here is what I found.
Works 'out of the box' at 4k with late 2012 rMBP via Accell adapter at 30hz For photo editing, this is just fine as nothing moves fast. For video editing its fine as well, but cant' see anything at 60p in real time if dealing with 60p footage.
On a Macbook mini mid 2013 i7, it only shows up as 1080p both on default HDMI port and via thunder port using Accell adapter. I have not been able to get the Mini to see it at full res.
There seem to be no reports that I've seen that detail getting it working at full res. Several people have comments like "Works great on my Mini" with no technical details so they may be 'ok' with 1080p
I have managed to screw up the settings on the mini using switchrex now to where it doesn't recognize the monitor at all

so will need to try and reset everything to factory on video settings.
If anyone HAS gotten this to work on a 2013 Mini (intel 4000) at full res, please post details!