The unit seems very sturdy, well made and durable. I made my first batch of yogurt according to the recipe in the enclosed book, and it came out great...very creamy and just mildly tangy. The only objection (and the reason for only 4 stars) is that the jars are not completely watertight...yogurt whey leaks out if the jar is placed in a lunch bag or other place where it might be tipped.
The recipe seems to make more yogurt than the jars can hold (particularly when adding a container of store-bought yogurt). As an experiment, I took the leftover yogurt mixture, put it in a container and stuck it on top of the hot water heater (one of several ways to make yogurt without a yogurt maker). The yogurt in the yogurt maker was far superior in consistency. I therefore think this was a worthwhile investment.