Kinda sucks, since I used to use it as an inaccurate indicator of time remaining while on battery. However, I can't pinpoint the time but I started just paying attention to the percentage and if it was dipping below a certain percentage I would charge it (generally if I'm at home this is 5-10%). I also pay attention to my iStats Menu at the top a lot more than I ever did the battery and usage feature built in.