First the good. It's a well-made product. It really does seal well. I've never had any problems with it leaking. You can throw it in a bag, leave it on it's side for hours - it just doesn't leak. It insulates well too. Coffee stays hot for hours. One-handed operation is easy, convenient, and works well.But I don't use it anymore because it makes my coffee taste horrible. Hand washing doesn't seem to help, although running it through the dishwasher does work better. So maybe it's my fault for not cleaning it thoroughly enough after each use. I just can't give it more than a few stars because my coffee always tastes horrible when I use this mug.