I am doing payroll processing with this software since 2004! It has been very reliable every time we use it to process our paychecks from my employer (who uses Paychex).
There are no problems that come up when using their service. They have always met or exceeded all expectations in terms of reliability at each step along way - setup/use; data entry & payment reconciliation issues during year end close out as well as tax reporting needs which can be quite complex but they get there quickly so you don't miss filing deadlines due date changes etc..