Bests & Worsts Reviews from Amazon

I just bought a Zircon StudSensor e50 and used it to find a space between wall studs so that I could install a small built-in shelf in a bathroom. The sensor is a little tricky to use, identifying studs in one slow pass and then not identifying the same ones in a second check-up pass. So, I spent quite a bit of time checking and rechecking until I had marked several positives in the same vertical planes at various heights. Now, sure of the spacing of the studs, and corroborating that they had the same spacing as the opened wall on the other side of the bathroom, I confidently started breaking up the plaster. You can guess what happened: The hole opened immediately to the right of an extra stud the sensor did not catch (apparently bracketing the iron ventilator pipe that the sensor also did not pick up on, which could be excused as it was about 2" behind the wall, just past the sensor's Deep Scan option's reach). So, caveat emptor: This sensor may have a tendency to false negatives, even despite several repeat passes in both Stud Scan and Deep Scan modes. I'm out $20, and a fun home improvement project has just become an unfun plaster repair project.