It kinda works fine when converting very simple USB-only controllers to MIDI DIN Out or when converting MIDI DIN In into USB-only devices.
Connecting it to USB-only devices that send out MIDI Clock/Sync msgs will hang it after a few seconds, so it's useless to convert USB MIDI devices like sequencers or drum-machines, like the (USB-only) Millenium MD-90 Mobile Drum, which was exactly why I bought the Miditech USB MIDI Host and it turned into a relatively expensive paperweight for me, since it's useless for what I wanted it for.
I also found out that it doesn't work with the latest Teenage Engineering OP-1 OS#243 firmware update. It does work with OP#242 ('OP-1 Midi Device MIDI 1' port), so I'm guessing it can't distinguish which of the 2 (renamed to 'OP-1 MIDI 1' and the new Audio 'OP-1') virtual device ports should connect to. It may be wrongly binding to the new Audio one now instead of the MIDI one, so it recognizes the connection (LED changes from RED to GREEN) but no data is transmitted to/from the MIDI DIN ports.
I ended up making my own custom made USB MIDI router out of a Raspberry Pi Zero and a powered USB HUB and an M-Audio MidAir interface but a wanted an even more compact and simpler solution which, unfortunately, the Miditech USB MIDI Host isn't and I ended up paying for it just to know that.
If MidiTech provides a firmware update that fixes these issues, then yeah, this would be a properly useful product. Until then, it's a paperweight :(