I like that it is very easy to use, you can create multiple reports with different filters easily which makes my job easier as an admin person who has many tasks at once! It would be great if they added more features such as creating custom fields or being able to add your own data sources so we could pull our payroll information from another system instead of using their provided one.
We are solving this problem by having all employees track vacation days online rather than manually entering them into excel files each week.