Very comprehensive and easy to use.
Just two problems: one, there is no way to add a line item at a negative value to indicate a discount, simply because that field doesnt offer the - character (whereas you can do this in a browser).
Two, it would be nice if the invoice memo field allowed you to separate lines of text with the return button, instead of forcing you to jam all service details into a dense paragraph.
All in all, though, great app.
lbht about Wave: Small Business Software, v1.4.0