Also a paying customer, I'd like it if they would email an invoice every month instead of me needing to go login to the web UI and dig for it when I do my monthly tax reporting.
1. Everyone make invoices PDF
2. Send them out every month
3. If I need to log in, make them easy to find on the first page
4. Name them <company>-<invoice>-<date>-<number>-<amount>.pdf
Thanks!