Multiple device support and history synchronization between devices really are table stakes to me, especially since I tend to spend a lot of time checking messages and chatting from mobile devices these days..

That distributed social network thing sounds quite exciting, and very much in a similar vein as Matrix. Does it have a website/github repo yet?

We've definitely found its not always easy to balance a philosophically pure/technically nice solution with one that actually has a usable UX. Although it sometimes seems that half the battle is figuring out what actually is a usable UX...