I don't think you can measure an OL's quality just by the number of sacks they give up. Sure, Fitzpatrick took fewer sacks last season, but if you look at QB hits, Fitzpatrick got hit 69 times compared to Brady's 71, with Brady getting 42 more pass attempts.
Sure, Fitzpatrick is pretty mobile and helps avoid some of those potential sacks, but how many times have we seen Fitzpatrick throw up a ball he should have just ate? Those INTs hurt a lot more than sacks.
There are a ton of different factors involved. The Bills rely on a quick passing game out of the spread and get rid of the ball quickly. That reduces the amount of time for the pass rushers. One could look at the numbers and say the OL is great. One might wonder if a big part of that approach in the passing game is because the line can't hold up.
Tom Brady was the 13th-most sacked QB in 2011 behind a high-quality OL that featured former Pro Bowlers at tackle and current Pro Bowlers at guard. He also averaged over 1.75 yards more per attempt than Fitzpatrick, so while Brady only had 42 more attempts, he threw for over 1,400 more yards. The Pats OL had to maintain protection a lot longer on those pass routes.
In 2012, Fitzpatrick has only been sacked once, and hit only 8 times. But the Bills have also changed their game plan. He's 27th in pass attempts after having the 6th-most attempts in 2011. He's thrown less than all the rookie starters except for Russell Wilson. He's done better with the fewer opportunities, and the Bills OL does look improved from last season, but they've also played the Jets (who have only 3 sacks so far, good for 30th in the league), the Chiefs WITHOUT Tamba Hali, and the Browns, who they beat with an extremely short passing game (averaged under 6 yards per attempt). To put that into perspective, only two teams allow fewer yards per attempt.
The Bills were precise enough to win, but it doesn't mean their OL is amazing. They are relying on the run and the short passing game. Whether that's due to their receivers, their lack of trust in Fitzpatrick, the inexperience at OL, or a combination of those things, it's clear we're not comparing apples to apples here, and I'm certainly not preparing to vote for the Bills OL for the Pro Bowl just yet...