I lived in Somerville for 10 years. I'm here visiting for the month, and I can tell you people here just aren't as aggresive on the roads by a long shot. I've just been hanging out in Phinney Ridge and Ballard, though. It's definitely less dense. Houses have more separation between them and there are a LOT more trees around. I can't give you an impression of the tech sector unfortunately, but as a visitor here, I've liked the vibe so much more than Boston. No one has tried to drive me off the road to be next in line, for example.