The worst part about the whole Spygate controversy is NFL Commissioner's Roger Goodell's attempt to cover up and sweep it all under the carpet. I can't imagine any other sport in which 7 years of blatant cheating by one team would go without a more serious penalty.
Here's what we know: Bill Belichick cheated in order to get an advantage on teams that would be played 2 times in the same year. Videos were made of the opposing teams signals on both offense and defense. These videos were then used for the next time the Patriots played the same team that year. This enabled the Patriots to correctly predict the plays of the opposing teams in some games. The full extent of which we don't know yet. Roger Goodell has made no attempt to determine this crucial fact. But some anecdotal evidence from one unnamed quarterback suggested it could have been as high as 70% of the plays from the opposing team.
Did this cheating help the Patriots win 3 Super Bowls: Undoubtedly. The taping goes back to 2000 and continued until 2007. The Pats won Super Bowls in 2002, 2004, and 2005. The only Super Bowl the Pats lost in this decade was this past year -- when the Patriots no longer were videotaping because they had finally been caught by the New York Jets.
Why doesn't Roger Gooddell do anything: It's against the self-interest of the NFL to expose the extensiveness of the New England Patriots cheating. Tom Brady and New England are marquee names for the NFL, and the whole Spygate saga threatens to unravel the entire mirage of the Golden Boy.
Why aren't more NFL teams complaining: Ditto the last comment. It's against their self-interest. The Patriots bring in money for the NFL. To tarnish their image would potentially hurt revenues.