Design looks great, though on the home page your two buttons are competing for attention. Ideally, have just a single button there. Or make one larger than the other. I think the homepage is too light to excite a potential customer. Also, somehow I have hard time distinguishing it from other invoicing apps. Maybe you would want to answer why is it different?

A small typo in your testimonial. Spelling of definitely here -> "definately switching to this"