Those layover times are really GREAT. I work hard to craft things like that. in Minneapolis you can check your carry-on in a locker and take the light rail from the airport downtown and/or to the Mall of America.

I have still never managed to do it in Detroit (either a sure bump or a standby has fallen though) but I am constantly renting cars in advance in anticipation, and if I ever get my long layover there I'm driving to Ann Arbor (though my brother keeps recommending the Henry Ford museum which I think is in Dearborn).

Admittedly, 8 hours in Amsterdam or Paris is preferable, but a free chance to see another corner of the world and sample the local nectar (particularly Bells beers in Michigan) are a bonus for me.