Bit of a me too post... but I find WebRTC options like palava.tv are the only ones I've really successfully used with others, because not many people that I'd ever video chat with use SIP/XMPP. (Though... I also don't have webcams on my main laptops, so I don't often video chat period.)

I'm running ejabberd for XMPP though. I have used that occasionally with my wife years back when we were both using N900 XMPP clients that supported video (Jingle I guess?).

I've got FreeSWITCH running for SIP... but it's mainly used to run the internal phone system at work. I find SIP is great for interfacing with traditional telephony, but I don't use it much for computer-to-computer communications... (again, don't know many people using it).

For voice chat though, I've used XMPP voice chat a long (as an alternative to roaming when travelling to call the wife at home), and I use SIP all the time (to call phone numbers, or to call other users in office through our phone system).