The Buffalo Bills won their preseason opener last night. They beat the Ravens 20-19. I didn't watch any of the game except for an excerpt of a couple of minutes while we stopped Mission: Impossible! for a bathroom break. Generally, I pay very little attention at all to the preseason. Why? Well, in 1990 the Bills went 0-4 in the preseason, while the New York Giants went 4-0. The two teams later met in the Super Bowl.
Preseason tells you nothing about how a team will perform. It also doesn't tell you much about the rookies who are trying to make the team. The only relevance preseason has is if your team's starting running back breaks his ankle or something. Then it's relevant. Outside of that, nope.