Q:

Cross-platform, decentralized (or available server daemon) IM/VoIP that's easy to use and actually works?

Given recent revelations about constant dragnet surveillance, I've decided to start looking for alternative forms of communication that let me be in control end-to-end.  My first step is to wean myself (and my family) off of Skype.
I've spent days searching, downloading, configuring and experimenting with various open source systems for IM and VoIP.  So far, I've installed and configured the Prosody XMPP/Jabber daemon on my Debian server.  It's reasonably simple to use; I just need to create the accounts for everyone and give them straight forward instructions for configuring their XMPP clients (probably Pidgin).
This works nicely for IM and file transfers, but that's the limit it so far.  If this is going to take off, I need to be able to do VoIP and, ideally, video chat.
Is there any IM and VoIP system that:

Has clients for Windows and Linux
Is encrypted end-to-end
Does IM, file transfers, VoIP and video chat without huge user configuration hassles
Is either decentralized or lets me run my own daemon

Pidgin is a nice client, but it appears to only support VoIP on Linux.
Jitsi is buggy on Windows XP, it won't launch unless the audio libraries are disabled, which obviously means VoIP won't work.
RetroShare is decentralized, but is far too complicated for most users to add new contacts.  VoIP is also highly experimental and basically useless at this point.
I'm open to pretty much any ideas that meet the bulleted criteria above.

A:

I'm a strong advocate of XMPP (previously known as Jabber), as it provides a lot of advantages:

Decentralized server
Open standards
Uses mail-like addresses (for most users, this is the same as their mail address)
Large potential user base, as many mail providers do include XMPP as part of their service (e.g., it is the technology behind Google Talk and Hangout, even though Google seems to want to undo their early openness)
Servers do cooperate if necessary (similar to Mail using SMTP: user1@domain1 can invite user2@domain2; only the two servers are involved)
Server is easily set up
Clients support IM, Audio, Video, Screen Sharing, shared Whiteboard, …
Many clients support end-to-end encryption and authentication (using OTR for text and ZRTP for A/V)

As a server, I recommend ejabberd, which many Linux distributions include as an optional package, as it is full-featured and easy to configure.
Clients galore, depending on your taste:

I personally prefer Jitsi, as it supports IM, A/V, Screen sharing, group chats (including A/V), by default secured by ZRTP (I am fearless enough to use their nightly builds)
Pidgin (MacOSX counterpart: Adium) is what many of my friends use.
Psi+ (the development branch of Psi) also has a great deal of followers

The best of it: Most clients have multi-platform support (MacOSX, Linux, Windows) and also support other IM protocols, so your friends can gradually be converted :-).

