Overall it was still a better showing than what the Bears D was able to put together last year. The O turned the ball over 3 times, the game went to OT, and the Bears still only gave up 23 points. Even though the Bills aren't the best offense in the league, they didn't torch the team through the air and they were only able to get 15 first downs during the game compared to the Bears 29. The D wasn't spectacular against the run, particularly if you factor in the game killer, but at least so far it wasn't an open gate; until that final run the Bills were at about 4.7 ypc.
That's not the best defense in the league, but so far thats a major improvement from last year.