Yes, poor Jingle support really puzzles me. It's not new, but I barely ever manage to connect two different clients without problems for video calls. That's besides the fact that most clients don't support it at all yet...
I don't have much respect for Hangouts really. If Google wanted to improve things they could propose Hangouts protocol as a replacement for XMPP. Make it an open IETF standard. They were such backers of XMPP in the past. And what did they do instead? Another walled garden and proprietary protocol. Total failure Google. That was the point when I said - you are lying about not being evil.
My understanding for poor Jingle support is that, whereas text is easy and low-bandwidth (so you can afford to send everything through a 3rd party server with easy connection semantics), voice and video are much, much much more complicated: not only do you have multiple voice and video codecs with iffy support and stability (sure, even if support library claims to support CodecFoo, it may still fail when passed data from your peer that uses this other library), but the bandwidth requirements means that you now have to deal with trying to directly connect these two clients despite any silent NAT or firewall that may be hidden around. Jingle provided its NAT-traversal algorithm, but even that required network support in the form of "superservers" for when all else failed.
I don't have much respect for Hangouts really. If Google wanted to improve things they could propose Hangouts protocol as a replacement for XMPP. Make it an open IETF standard. They were such backers of XMPP in the past. And what did they do instead? Another walled garden and proprietary protocol. Total failure Google. That was the point when I said - you are lying about not being evil.