First, bravo for making it happen in a way that is getting people excited. Second, I sincerely wish you the best luck in getting people to pay for it in a way that is sustainable for a business. We built a user interface that made truly secure group file sharing accessible to mere mortals and said mortals were uninterested.
About three months after we shut down the business Edward Snowden made his infamous leak(s) and it became obvious to me that commercial crypto products coming out of the United States would be met with extreme levels of skepticism for some time to come. Any remotely centralized solution to the problems of key distribution and encryption are probably dead on arrival because of the single point of jurisdiction/political failure. It really doesn't matter how open you are (unfortunately).
Two things really stand out to me about this implementation. 1) The trustworthiness of the key exchange doesn't appear to employ a mechanism that protects against a man in the middle. 2) They mention the possibility of in-browser Javascript crypto. These are not small issues. The people who need crypto require rigid, durable implementations that don't gloss over security concerns in favor of usability. Everyone else is just being trendy.
I wish you the best of luck.