Wow. Barack Obama is literally relocating huge swathes of the DNC to Chicago. Ambinder points out that this is more like a continuation of trends from previous cycles than a sharp break with the past, but it's still a noteworthy change.
In general, I think it's smart for campaigns to get out of the DC/Arlington that McCain (and Clinton before him) are operating in. Political junkies have a very distorted view of events (usually massively overrating the importance of everything that happens), and I would imagine that shifting to a location that's not lousy with 'em helps people keep some perspective on things.