Would be five if...

The following features were implemented: enter sleep start time and wake time and have the app do the math. Someone commented that the slider is awkward, and I agree. An export data to .csv feature would be nice, bit only because I am a geek. What I like: the goal sleep time feature. I think the graphical display is good and love that you can make notes and rate the quality of sleep. This way, you can look back and see if there are periods of poor sleep and remember why. For instance, I tend to sleep poorly within a week of a full moon (weird, I know), with these features, I am now able to see patterns and adjust my schedule accordingly in the future.

Bleed242 about SleepLog - daily sleep journal