I had it route me from Letchworth State Park, NY to Lewiston Ny and it added about 50miles (50% more)to the route vs a more direct route. It is basicly North West. Google had the route going North East until it reached the Erie Canal Path and then heading west.
Google bicycling routing seems to over prefer trails to roads so much so that it will add over 50% to the distance to travel just to use the trail.
Google maps street view is very helpful to confirm that the item(campground, store, ect) is actually where the map says it is or that the road exists.
It is nice to actually find trails with, but I will keep using Delorme's TOPO to do my routing. I can add the trails found in Google to delorme when they actually help.