I'd love to be able to customize the invoice a tiny bit (for example, I don't like the small size of the logo and the fact it's on the bottom, even though it appears on top in the editing screen). One more request is the ability to use the same notes / footer on every invoice (for bank info and the like), now I have to keep my bank info in a separate place and copy paste it each time I make an invoice.
With that said, this software is free, reliable and looks good so the shortcomings really are forgivable. Would still be nice if it got improved though :) thanks for making this!