looks like a rather better version of the trailgator and its friends - I think the main thing is to get the right amount of rigidity/flexibility between the leading bike and the led bike.
I've never tried one. I'd expect it to feel 'worse' than a trailerbike attached to the seatpost in the same way as the latter is 'worse' than a trailerbike attached to a dedicated rack and behind the back wheel (the latter 2 which I have tried).
So that wasn't very much help.