I like that they are always trying to improve their app so it can be more user friendly.
The fact that you have to pay extra money if your invoice gets rejected because someone else has already paid them first makes me think twice about using this service! It's not worth paying an additional fee when there should be no reason why my invoices get denied in the 1st place (the person who pays doesn't want/need what i'm providing). Try out other apps before deciding which one works best with your business needs. They offer many different types of services such as logo design, website development etc.