I like that everything can be done via one website so there's no need to go back & forth between different websites or emails - it makes my life easier as an owner! It also has many other features such shipping rates calculators which helps me determine if certain products are worth their cost compared at what they currently sell per unit/pound etc..
The only thing i don't really have much use out off yet but am hoping will come up soon would maybe help when sending invoices through paypal? Also wish you could add more warehouses around your area depending how big / small business size was this might not apply though because we do ship internationally now however having extra options within our own country should always beneficial too :) Currently using them mostly just doing some basic calculations before placing orders then once placed all notifications sent over email automatically without needing any action needed from myself unless something goes.