Health food stores and some health food sections of supermarkets carry it. I don't use it coffee, but I put it in iced tea and aguas frescas amongst other things. It works fine if I use a bit of sugar to get the right mouthfeel.
The only sweetener I use regularly is in my coffee. I always thought that my abilities to detect sweetness was very good. I liked the idea of using stevia very much but alas I cannot taste anything in stevia.