I have one. What you have to keep in mind with this one is you don't read negative densities directly the way you would with a regular transmission densitometer. Instead the process involves your enlarging paper and making projection readings.
It can seem laborious at first, but what's nice about it is it forces you not only to develop negatives, but to evaluate how the densities actually print. This is what we should all be doing anyway of course, but with a regular B&W transmission densitometer it is easy to get carried away just measuring negative densities and calibrating to typical ZS guidelines in order to determine working EI, development times etc without actually seeing how they print with our own enlarger on our chosen paper.