Check progress here:
http://boharald.blogspot.com/2009/05/consumer-e-invoicing-making-great.html
Really important to provide same user experience for private-role and SME-role receivers and senders. And naturally the same tool when billing consumers and enterprises.
A rising number of receivers are already starting to not-buy if e-invoice is not offered. Once one-click payment is tried - it becomes next-to default.