This is fascinating to hear. I'm curious: did the open-plan office have private spaces available for when you needed them?

  >  I now make it a point to walk around the halls and 
  > drop in on people who are open to it (green status 
  > light on the door).

That's funny and interesting that they have actual lights on their doors. When I ran my own consulting thing and worked from home a lot (often at odd hours) my partner and I joked about having a radio-style "ON AIR" light above the door so she'd know when I was working; sounds like Microsoft is actually doing something like that!

In offices with "normal" doors sans lights I usually just use the time-honored system: completely shut door means "please don't interrupt unless you're telling me the building is on fire," a completely open door means it's party time, and if my door is open just a crack that means I'm working but you can come in and talk if you need me.

Not everyone has them, they're called the "Blynclight." They just sit outside your door and light up with the same color as your status in Microsoft Lync (red = busy, yellow = away, green = available). If you're in a Lync meeting, or on the phone, or have set "do not disturb," your light will be red.

The problem with that is that getting interrupted with an instant message isn't usually as bad as getting interrupted in person: I always turn all the IM notifications down to a minimum and so the only change will be a new color on the icon which I tend to notice in a couple minutes.

Sounds like a win-win to me. You can drop in on people who welcome interruptions and others can get their work done.

And people can change the status according to their current needs without any hassle. Perfect.

See, now, I had heard that Microsoft was moving to open "team" sections? Was that just for the Visual Studio guys and such? I'm a huge fan of team zones where everyone in the same area works on the same immediate issues, and can also get some privacy and quite time etc.