Intuitive, clean and easy to use UI (user interface). Powerfull app.

On top of this, the app works like a charm, no crashes.
Developpers are helpful and prompt in their replies, either to assist you or to add any improvements.

This is what you were looking for your home-office, office or studio for billing and invoicing: small footprint in terms of hardware resources, great integration with other OS services, easy to use, fantastice price.

Mac developpers should put their eye on this software and follow this developpers example.

Six stars!