I like that it's very easy to use, has all of our employee data in one place including payroll information! It makes tracking time off requests much easier than with Excel or paper calendars for example--it literally takes seconds versus minutes per request/update.
We have used this program since its inception about 6 years ago so there isn't anything new we really dislike at present (and nothing you can do without some customization). What made us decide against using other programs was their ability to create user accounts within 1-2 hours which allowed many employees access but didn't require them pay $150+ every year just because they had more people working under them; instead allowing each person who needed additional login privileges only need purchase those services once rather than having multiple copies floating around if not monitored and updated by admin staff as necessary.