I use both, Auto Sleep, and Sleepwatch, and honestly, they both are "sometimes accurate, sometimes on drugs" it would seem. I think both apps have a "mood", as on some mornings, they are right on, and on others, they're way off, I mean like 30 minutes to an hour. The graphs are pretty, and the things are somewhat useful, as long as you realize the days that they're not accurate, or so it would seem.
I charge my AW in the mornings, during coffee, and while I cruise the Internet. I'm retired, so I don't have to be bothered with having to be anywhere (like Work - UGH) at any given time. 🙂