I like the easy data input, which resembles a spreadsheet style layout (great for finance folks!), the system is easy enough to use (simple logics, easy formulas for new codes), I also like the email statement delivery (better than paper statement of earnings or logging into other services, or even the website itself to get statements), and I also like the ease of reporting - I can easily design reports or request help, and their team is friendly and easy to work with, should I have any requests.
I also love their fee structure. It's simple without all the nickel and diming that is so prevalent with other providers. Review collected by and hosted on G2.com.