if the matrix guy can read this, it's important, make things mean and lean.. not overly powerful to the point of alienating the mass market. Maybe have an expert mode for that.
This. Using the app should be dead simple - with a default server, a default username, maybe even a pre set password (bound to the phone number or whatever, I'm not a fan of this but they all do it this way) and a feature adding contacts via link, qrcode, or phone-number. And then there should be a button for expert-mode giving you the complicated setup you want - choosing your own server, name, password and whatever.