I didn’t go downtown during the G20, but I live in a neighborhood about 10 minutes from downtown. I think the biggest change was that it was much quieter than usual – a lot of Pittsburghers who didn’t need to be here took the opportunity to get out of town for the weekend, because they knew the security was going to make things a little crazy. Those of us who stayed in town stuck pretty close to home, so the only thing we really noticed was the abundance of police, sirens and helicopters, like @deni said. We kept track of what was going on with the protests and road detours and closures via twitter, and just made sure we steered clear of the hullabaloo.
I think for people who were more involved in the summit there was more of an excitement to it – and I think we were all pretty proud of our city (even those of us who avoided getting caught up in the action!)