The ease of use! I was able to set up my account within minutes, after which it has been easy from there - no problems at all using this product so far. It helps me keep track of client payments with one click instead of having multiple email accounts open or going through file folders looking for receipts etc., plus everything is saved online allowing quick access when needed. Very convenient way to invoice customers as well. Nothing much yet but have noticed that sometimes some information might be missing such as amount paid by customer (i'm not sure if they're just hiding them because you can't see those amounts). Also would like more options regarding how often emails are sent out but overall very happy about greenerbilling!! Great tool for keeping tabs on payment history/receipts without having to go back over files manually.- Keeping an eye on current bills- Invoice customers quickly- Easy to send reminders via e.