I sat it row 25, 15 yard line for years. Great view of the action on that end..and you could hear the crunch and see the player's eyes. But on the other side of the 50 the view got progressively worse...particularly in the Red Zone.
I have buddies in Row 2 behind the visitor's bench...and though it's cool, more than 20 yards away it's just a mass of bodies. But they love it.
I'm in Row 40 now and think it's about perfect.
And I know folks above the entry tunnels...one in Row 52 and one up much higher and they love the view they get of the plays developing.
It's all personal preference. The closer you get the more intensity you'll feel...but the less of a "TV" view you get of the plays. It is cool though watching a guy crash into the defender and shed him...or a guy leaping across into the endzone if you're in Row 5 near the goal line.