The interfaces seem like a gross rip off to me, and I won't be throwing cash at one until they drops in price. Maybe you could get the Nitek Duo interface cheaper, same computer?
Also there are details for a DIY interface avilable -
Daniel's website
I keep on meaning to take a closer look, but haven't quite got round to it, I'd like an interface for the "Toy" factor, but not enough to spend ~£70!