I've had this mug for about 18 months now.  I love it and use it basically every day.  I have a charger at home and one at work and that keeps my mug charged and warming all day.  I'm very disappointed in the leak proof lid, however.  Mine does not pop up and down anymore.  It's stuck in the closed position so I have to use my ceramic lid which does not keep the heat in.  I tried to find a replacement, but Ember does not offer one.  VERY disappointing, especially for a product at this price point.