- The killer app in this space is whether you have an answer to "Why can a startup displace the incumbents?" and "How are you going to get people using this?" The answer to the second must be understandable by my dry cleaner, who would not trust bitcoin even if it were issued by the US Treasury. The prototype at this stage is probably about as useful as PayPal's first prototype (which was for a different idea, IIRC). Edit: not hating on Bitcoin, just pointing out that success here will derive in part from expanding its use beyond the core early adopters.
- Work on your writing & proofing. It may seem petty, but you're aiming big so this stuff matters. People (cofounders included) will pay attention to sloppy writing at this stage, using it as a proxy for information they don't yet have about you. Plus, when my cofounder emails senior people at major banks, will I feel compelled to rewrite the emails? Temp accounts plus poor writing => no response.
Hope this helps, and good luck.