Well I wouldn't just call it an interest in my case. It certainly is, yet it's more than that by being a survival need where I live unfortunately. And when I say "survival" I mean actual "life", not just cyber privacy.
But really I'm not an expert, nor am even a developer. I'm someone who needs to know security to protect myself and some others close to me.
I asked those questions just to be sure, not to undermine your efforts in anyway. I have the deepest respect for people who work in this field, such as yourselves.
As far as my inexperienced input on the multi-device feature, I'm not particularly interested in this feature and I suggest you think very deeply about implementing it as securely as possible; not just technically, but from a social standpoint as well. I would actually be worried if it was implemented as I can't particularly verify that the person I'm talking with isn't compromised himself. I may be technically inclined not to get compromised easily (in theory), but I understand that who I'm talking with isn't as techy, for example, as the other party in the conversation.
With that said, I hope to see a way of sharing the key over LAN network or some other way that doesn't involve sharing it over the Internet whatsoever, even though I understand it's encrypted. The problem I see is that we can't fully understand the capabilities of those interested in mass surveillance or even those who might abuse the legal system to get what they want from your servers (getting the key is the first step in breaking that user's security).
There's also the aspect of user error. If it's encrypted by the user's own secret key, this brings all risks associated with putting that info at the hand of the user; from social engineering attacks to even simple brute forcing of weak passwords after requesting the key from the server. So I'm all for decreasing the attack surface as much as possible.
Good luck, guys, and keep up your dedication.