I love the Ember mugs and have many of them. There are a couple of things that are really annoying. The first and biggest is that the coasters die so easily. Even with lots of care, and I am very very careful, the pins get messed up and the coaster no longer works to properly charge the mugs after a while. They aren't cheap and the mug is best appreciated with you have multiple coasters set around where you are going to use it. Instead of having extra coasters because I have extra mugs and have purchased additional coasters, I end up having to buy more just to keep one working. The other major annoyance is how frustrating the app is to use. But I could deal with that if they would just fix the coaster problem.