(Author, here) Regarding #1 and #2, I have to say that one of the most surprising things about Google Hangouts is that they've really make it easy to... hang out! It's pretty standard on Fridays (or during the week) to kick back for an hour or two and just talk in the hangout. A lot of people just keep it open sort of half-listening while they work, and if they need to do something that requires a lot of concentration, they just drop out. In fact, I have it open right now and all I hear is a bit of breathing and typing...
You have to think about it differently than "Oh, we go here for meetings". It's more like a watercooler -- pop in every now and then and see what's going on.