I like that it is easy for people who are not tech savvy or computer literate to use! It makes keeping track very simple with an overview page being able to show you what services have been paid in full as well as those which still need payment/satisfaction from clients via reminder emails when due dates approach etc (which helps with client follow up!).
Also great if there's no internet access - offline reminders work perfectly too!! Nothing really so far but would be nice having some sort of mobile app version added one day perhaps? We've just started using this software last month after deciding against another system we were looking into previously- however now realise how much better our workflow has become since switching over!