If good, stable textual communication across every platform that matters is your goal there is a reason IRC is still a thing where other things have fallen by the wayside. It does not do voice, video and files (see DCC) can be a pain for some but it does group text, individual text and more quite well with security there if you are willing to put in the effort, all with a thousand different clients for those that want that, an uncountable number of servers (and the option to make your own if you really want) and no chance of it all being folded into something else. In fact the only thing I like more from a usability standpoint is the tencent/QQ setup (what China uses instead of facebook and similar such sites) which does images, stores text for offline sending by default and integrates tightly with email. Time was I might have offered up XMPP (what google talk kind of once used) but I am not sure I can today.
Possible alternative alternative. Teamviewer. It is on basically every platform, does screen sharing/conferencing, has pretty decent text, video and audio and can also do all it does with the remote control options, vpn and such like if you want it.
Alas it does make for fairly painless video chat so I have to continue to suffer it/support it for others.
