Yeah given that the new Hangouts is a proprietary closed protocol (as far as I know) I don't think it's possible for third party to fully integrate. Their site has the Hangout logo and says Hangout on the feature list which gave me a bit of hope. But if you scroll down it actually says it supports Google Talk instead of Hangout.

Yep, it is a closed API. A bit annoying, but I much prefer desktop clients over web applications or browser plugins, that's just personal preference though.

Yeah I do prefer desktop clients over web apps and browser plugins. But I do do not want to have to mark messages as read twice, once on my computer and again on my phone which is why I tolerate the Chrome Hangout plugin.