I did it last year as my first marathon and I'm doing it again this year.
It's a big enough race where you are running with people all along the way, but never so many that you are crowded. Many spectators - You cross the bridge over the Detroit river into Canada and the crowds are lining the streets- music blaring- it is awesome foresure... then back intot the US through the tunnel (lined with customs agents to make sure no one "sneaks" in the country) and when you exit that tunnel into the US there are MASSIVE crowds, live bands.. its really something else. Total positive experience. Do the race - you won't be dissapointed. Plus its a great course for a PR. Cool weather, flat.
http://j-motrilife.blogspot.com/