You're supposed to understand the different colors of the lines. I haven't taken the time to memorize what color means what. Yea, they are smushed, but I like how is a Battery % vs Time graph and shows you how fast it goes down in 10% increments. If you run your finger over a certain time, it'll show you what type of data connection it had, whether it was plugged in or not, etc.
BatteryLeft is awful for me, it has been calibrated and it's a good 15-20% off on its approximations. Maybe I am doing something, wrong, I don't know--but it's near useless for me.