I used one initially, but ultimately switched it out for something else. There have definitely been some horror stories with them (especially with the version 1 units), but there are also plenty of people that haven't had any issues. One issue I noticed with mine is that it couldn't dose in 1ml increments properly, so I calibrated it at 50% and that did the trick. Overall, it was a decent doser for my use initially.
With that being said, I wouldn't trust this unit at all without some type of failsafe in place. I refuse to lose thousands of dollars in livestock to a $60 doser. For me, this was as simple as only providing the outlet with power for 12 seconds at a clip at my dosing intervals. It takes about 5 seconds to power up, 5 seconds to dose my increments, then another 2 seconds for buffer. It has an internal battery, so the doser will retain the current time, even after coming back on. This doesn't make it a perfect solution by any stretch, but I'd much rather have it miss a dose than dump a gallon of alk into my reef.