After using the software I think that it is good, but he lacks several things that later I detail.

1- The possibility of adding a text in the e-mail before the invoice. that should use as introduction to the invoice sent in the e-mail.
Alone sending the invoice to the client? It would not be it better be able to add a message in the e-mail before the invoice?. Probably they will say to me, for it the notes are. But the ideal thing would be a text before showing the invoice that makes clear that it is (that alone appears in the e-mail).

2- remember of payment. The people not pay with an unique notice. Every x days it should be able to send a remember payment At least two notices..

3- I have possibility of using cron task. Such that automatically generates the renovations. The idea is the independence of the management of invoices in what it is possible.

4- The possibility of creating quotes. Gentlemen .. quotes .. slightly super basic that you already have made. A quote is an invoice without obligation of payment that can transform in an invoice.

Does someone more share my suggestions?