I too invested in this combo — generally putting it then into a Blackmagic Video Assist for recording. And have also had good results.
Sometimes they don’t like it when I put very glitchy signals into them and I end up with some blue screens, but that is certainly to be expected. And I would say it is probably as/more stable under those conditions than any other analog-to-digital conversion system I’ve tried.
Bought all three used for well below list price. But, yeah, the UpDownCross HD was definitely the hardest to find secondhand (Ebay saved searches/alerts helped).