What are you talking about ? Invoicing is for getting paid. Why waste time trying to impress some AP clerk with your fancy stuff
I agree, though. GnuCash has a ways to go. You can customize your own invoices with fonts, graphics,logo's etc. Take another look.
I refuse to run a windows computer for quickbooks. I'll live with GnuCash. Actually, it is kinda charming in its own way.
There are other threads on LQ which ask the same question as yours, with fuller responses.
There is my two cents.