(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.
I'm glad to hear I'm not the only one doing this. A colleague and I run a hangout most of every day, and it really makes it feel a lot like being in the same room. (I had to ask the other day -- "Is that your doorbell or my doorbell?) We can quickly ask one-off questions, have impromptu show-and-tell sessions, and of course engage in random brainstorming and "water cooler" talk. It's also easy to tell if the other person is deep in the zone before interrupting.
I've been using a hangout-like tool called Sococo Teamspace (I wrote part of it). It combines video, audio, screen sharing and chat, and you keep it open all day. It has the advantage that you can see who's in all the company-related spaces, who's sharing with whom right now. You can see if the standup is starting by who's in the standup space. You can chat with Bob who's late because he's talking with Tom in his office, by P2P chatting "Hey? Coming to standup?" without interrupting.
The real juice is removing the friction to communicating. You don't want to be scheduling conference calls or chatfests. You want to be able to click see if Bob's available, click into his space and say "Hey Bob, got a minute?"
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.