+1 on the comments that DTW is a fine place for a layover. It is my favorite hub too to be "stuck" at.

The central SkyClub in the A gates have lockers so you can drop your stuff off. This is usually my first stop so I don't have to lug it allaround.

The Westin gym pass is nice, especially if you are like me and will feel like a lump after sitting on an airplane all day. (Be sure to not trade in your ID for the locker key, you will need it to get back through security, of course! ) You also get access to the pool and hot tub if you're interested in a soak.

The tunnel is fun, the B/C concourse is usually quieter and it has stores that are not found in A. Fuddruckers is my favorite...hey I didn't go to the gym for nothing!

Using the showers was suggested and I was blown away by how nice they are. Clean, modern and spacious. They had done a great job at keeping them up and I was very impressed.

Of course you could always lounge next to the huge second floor windows overlooking the main entrance, snickering at the peasents as they scurry about while you relax, sipping on your favorite libation. That may just be me, though.