I'm with this guy, it alternate-routed me around traffic in Seattle a few weeks ago. Without a question saved me lots of time, and I wasn't the only one snaking down that same exact route.

(There was an accident on interstate 5 south, the backup was obviously affecting traffic on the highway but also the surface streets leading up to the onramp. GMaps had the most direct route, of following the traffic to the nearest ramp as the alternate route, with the default route being a snaking journey down some streets to the next ramp that was beyond the traffic.)