We love ours, and Jake recommends it to others very often. We have the 825. We love that it has 21 different levels (although we havent gone higher than a 3), a vibrate, and tone functions. Training with it has made Bacon nearly 100% on Recall, with just the tone.
We have never had an issue with ours, and Jake has never heard a complaint from anyone he has sold one to. If you to have an issue they have great customer service.