Delta times many of its flights to arrive about 15 minutes before the scheduled arrival time, presumably to increase its ontime arrival statistics. That means that in all likelihood you'll arrive in DTW about 45 minutes before your next flight. Even with the tram shut down, DTW is a relatively quick airport to navigate, so I've booked -- and never yet missed -- many flights there with 35-minute connections. That being said, as ethernal pointed out above, my calculus is very different if I'm connecting in DTW to an airport in Chicago -- where if I miss the flight I can catch another one in a couple of hours -- compared with connecting to an international flight, where missing the flight might have me stuck in DTW for 24 hours.