It should be kept in mind that BambooInvoice is open source, and if my experience modifying the appearance of the PDF output is any indication, it should not be all that difficult to modify in other ways.

My invoices, while not numerous, tend to have a lot of line items on them, so if your friend needs to issue 3-4 invoices per day with only a few line items each, BambooInvoice might just do the trick. :)