I haven't used their service and won't until they get a few years history. As a new untested company, it's like putting you money in a small offshore bank with no government guarantees. They exist by using the 'float' to generate income. If they don't make enough off this, they will disappear and your money will as well.

This would have been a great idea if initiated by an established bank with a reputation. For now, I will watch with interest. The service is one that is needed.