I have been using Billie since the earliest beta versions, and I have to say it has come a very long way.
At the moment it definitely speeds up my invoice organising task, with about 1 or 2 invoices not being able to be scanned on a batch of 20 documents, but with the latest version you can rename it within the app (very good improvement)
The playful feel of the app, the little ticket coming from the top, is a delight to see in these days of "all apps look the same".
I've contacted the developer a few times for support and he was very quick & friendly to reply.
Keep up the good work, I will certainly continue to use it!
