It took time to get it going - but this is looking good (statistics covers only Finvoice - similar growth in other local standards). In a couple of years time paper or e-mailed PDF invoices will be as rare as cheques (defacto not used since years).
More interesting statistics here: http://www.fkl.fi/en/material/statistics/Statistics/Statistics_banks_payment_systems_2001-2010.pdf