The only way I've been able to get into the new chat is with the guest button.
I don't see this as a problem, but neither the Tumblr or Twitter buttons allow me to actually get into the chat.
The external window opens, and I click 'Allow', and then it just sits there, the only thing you can do is hit cancel.
It acts like it's trying to hit the external site for verification, but it never happens.
I didn't try the Facebook button, because I dropped them a couple years ago after making the switch to G+. I view FB connecting with people that I no longer really give a crap about, whereas G+ I view as connecting with new people that have the same interests as myself.
Of course, my choice would be a real IRC channel on either Freenode or some other high-availability server, since then we could use Mirc, Pirch, XChat, etc.