That's the whole bar? The portion sizes listed on most of the dark chocolate I eat is between 160 and 250 calories, at around 40g, and the whole bar is usually 100g. In and of itself, I'd say its not unhealthy, nor are the calories excessive. However, this is relative to the quantity and quality of the rest of your diet. I average around 2200 calories a day, and go with a half-serving of dark chocolate (~20g), usually with some fresh berries (~100g)and/or 5oz red wine. Since you are doing it every other day, it averages out to about the same as me, so I certianly wouldn't consider it unhealthy. As long as it isn't interfering with your goals, I'd call it a reasonable indulgence.