The ease of use! It's so easy to set up your accounts that you can do them yourself in about 5 minutes (if it takes longer than this then I'm not doing something right). There is no limit at all as far too many features are available with an unlimited number or levels which makes life easier when looking through invoices etc., especially if they have been sent out by another business/company who has used other products before & will be familiar enough to know what needs done next time around…