Used to track your PTO (paid time off) on your phone. Recent upgrade includes the ability to track multiple types of PTO. So you'll be able to see how taking a vacation day next Tuesday might affect your vacation time for that big trip next year.
What does it provide over the free version?
1) No ads. It doesn't even have the Internet permission.
2) A widget where you can see your PTO on your homescreen.
3) The ability to track multiple types of PTO (free version only tracks one).
And some future enhancements may be "pro only", although I don't know what those are at this time.
Here are some screenshots. They're a mix of ICS and Gingerbread screenshots.