I was an early adopter of the Anova One circulator (October 2013) and have been extremely happy with its performance ever since. With my quality assurance background, I frequently check the temperature of the water bath as measured by two different Thermapens and a type K thermocouple and always found the temperature within a fraction of a degree of the Anova’s readout. I have used it very heavily (I’d estimate five times per week) and many times for products requiring 24 - 72 hour cook times without any issues. I was so happy with it that I ordered an Anova Precision Cooker as soon as it became available on Kickstarter, so that I could run two baths at different temperatures simultaneously.
Recently on very rare occasions the Anova One would blow a fuse. It’s very easy to replace (and there is a holder for a spare fuse on the fuse housing), but just to make sure that it was not a serious problem, I referred it to customer service. I got an extremely prompt response from them (Marilette Antonio) with an attached Fed Ex label to return it. As soon as I gave them the Fed Ex shipment number for the return shipment, they sent a replacement unit, without any hassle, without waiting to receive and inspect the returned unit or jumping through any other hoops.
It really doesn’t get much better than that.