All other critiques aside, it's telling that any users are coming to this conclusion because for me, a huge part of moving to GTalk/Hangouts back in 2006 or so was that I didn't need to install another IM app. I typically kept/keep Gmail open in a tab whenever I'm at my computer and it was great to not worry about Trillian or ICQ or AIM or any of those. When I was working at low-level jobs right out of college it wasn't always permitted or feasible to install applications like that on shared computers anyway. In-browser chat was a godsend and I liked how I could add my AIM account back when that seemed to be one of the more popular IM options among my non-techie friends.

Honestly I think Gmail/GTalk owe a lot to AOL for allowing that interoperability. Sites like Facebook would never allow you to connect with Google+ and use a competitor's site to access their platform. It takes away their biggest advantages (critical mass and inertia).

But it's right after lunch and I'm getting off topic. Personally I still use Hangouts as my primary IM/chat platform because it doesn't seem to give my systems much of a performance hit and it lets me carry conversations between machines and my phone without having to install apps all over. I use Pidgin at work but for everything else, Hangouts is still my default. Doesn't mean I'd mind performance improvements though.