I tried it out a few months back when I had an interesting exchange on Twitter with Jason Evanish (@Evanish). Check it out here: http://branch.com/b/who-will-pave-the-way-for-future-human-s.... Being able to import our back and forth on Twitter into a discussion was pretty slick since Twitter isn't very good at managing a back and forth when another person wants to get involved.
Everything seemed cool up until that point. I then invited some folks who I thought might want to chat about and have something to say on the subject matter, a couple of my co-founders and Hiten Shah who works with Jason. The invitation process seemed so spammy to me though. It sent a Twitter @ mention to everyone and without any context, it just felt forced. A few people asked to join the conversation and I approved them in order to see if we could get something going, but none of them ever responded at all.
Perhaps if I had a larger network of people in the know about Branch it would've worked better. I definitely like the idea of it and the execution is close, in my opinion.