I had heard very few bad remarks about this place so I had to visit even though I grew up a Chicago Bears fan living in Detroit.
I chose upper level seats because I wasn't sure if I was ready to shell out $100 on a lower level ticket for a lowly Lions game vs. the Atlanta Falcons. Section 321 kind of in the corner of the upper level but not quiet; it was still very much the endzone. My line of sight was excellent for my immediate side of the field, the opposite side of the field - not so much. But that's what you get in the endzone seats, a great view of only one side of the field. Best of all, I had row 3 so I didn't have a ton of stairs to climb and could easily get to the concourse area without trouble.

If you don't want to spend a ton of money on a hotel in downtown Detroit, I would recommend staying at the Hilton Garden Inn. You can easily walk to and from the hotel to either Comerica Park, Ford Field and area restaurants.