I was the one that made us support this, but alas I do not own one. I just found it a good and cheap solution to get a single channel SDI fill and key out from a laptop without a Thunderbolt interface.
AFAIK the quality is good. The way it outputs the fill and key is very clever. It comes from the fact, that broadcast video used the YUV color model with a reduced resolution for U and V. This is sometimes refereed to as 4:2:2. In contrast to it computer graphics uses RGB in full resolution on all color channels. So if you will you have 4:4:4. By using only 2 of the 3 color channels, one for the Y (4) and one for a combination of U and V (2+2=4) you end up with a spare color channel to output the key (also 4). That is all the magic.
What is a bit strange is, that it only has a SDI in to use as a reference and not the usual black-burst composite video. But that should not be a problem, that can not be solved.