I've been through Detroit, but never spent much time there. It was usually when we were on our way home (we were living in upstate NY at the time). We had relatives around Holland MI, as well as Indiana, Illinois, Wisconsin, Minnesota - kind of scattered all over the place. Went through the Detroit-Windsor Tunnel a few times - which allowed us to avoid Cleveland.
Not sure about Flint or Saginaw, but I've been through some pretty nasty cities across the country. A lot of depressed areas across the Rust Belt, Appalachia, and all across the southern tier of the US.