He's been good, but not great. I'd still probably take him over anyone in the league, but that aura of "Belichick the Mastermind Talent Evaluator" has worn off with some poor drafts from 06-08 and some poor signings.
The drafts from 06-08 killed this team. To get virtually nothing out of Wheatley, Crable, Meriweather, Maroney, and Chad Jackson set the team back. 06-08 was a key period for this team to try to reload while it still had veteran talent. Guys like Vrabel, Bruschi, Harrison were nearing the end but you figured they still had a few more years left and the young kids could develop under them and eventually take over. But it didn't happen. None of those guys adequately filled the shoes of the guys that left/retired/were dealt, and this team was left with a significant talent drain, especially on defense. The only good player they came away with was Mayo, who was a top ten pick. Even the 2009 draft which at first looked pretty promising has turned out to be pretty disappointing. We all had higher hopes for Brace, Butler, and Tate. Chung and Vollmer were good pickups, but Brace, Butler, and Tate all look like pretty bad misses, especially when you see Mike Wallace went a pick after Tate.
When you go back an look at those drafts, you're just left with so many what-ifs and what could have been. What if instead of Maroney and Chad Jackson they came away with Maurice Jones Drew and Greg Jennings or Brandon Marshall? What if they took Jon Beason, David Harris, or Lamar Woodley in 07 instead of Meriweather? What if we took Wallace instead of Tate in 08? Of course hindsight is 20/20, but the talent was there. Bill just missed out on it.
You can say that Bill has no one to blame but himself -- after all he is the one who tried to replace Asante with Fernando Bryant and Delthea O'Neal then followed it up with Wheatley/Wilhite/Butler in the draft before finally getting McCourty. He is the one that traded Seymour -- one of the cornerstones of our defense and one of the best defensive lineman in all of football -- and never really replaced him over a two year period until he traded for Haynesworth this off-season. And he is the one who has only drafted a linebacker once in the first round during his tenure in NE and never drafted pass rusher in the first or even developed one from the draft.
But even so, not many people have been better than Bill when it comes to drafting. He's had his share of bad picks, and the law of averages really caught up with the Pats later in the decade after they killed it in the draft earlier in the decade. He's the best in the business at collecting draft picks and turning current picks into higher picks the following year.
The only complaints that I've had are the reluctance to trade up and grab an elite player every once in a while and the lack of drafting/developing the front 7. Not saying he should do it every year, but when you have so many draft assets year in and year out, sometimes you've got to cash them and go up and get your Demarcus Ware type of OLB or Richard Seymour type of DL. I also think Bill has been far too passive in rebuilding the front 7. Besides Mayo and Wilfork, Bill has not invested heavily enough in the front 7 and it's showed in recent years. The linebacking corps and the defensive line have both lacked playmakers and the pass rush has been subpar. Imagine they went Beason in 07 and Mayo in 08? You'd be set at LB for at least the next 5-7 years while also giving them time to learn under a veteran like Bruschi.
Bill has been so good in the first round throughout his tenure in New England that you wonder why he hasn't traded up a bit more. A lot of people are afraid of trading up and giving up the assets and then being saddled with a bust. But with BB's track record in the first round, I'd say it's 90-10 or 80-20 at the worst that you're going to get a great football player.
2008 is the perfect example. Look at all the trash around Jerod Mayo -- Gholston, Harvey, Chris Williams, Gosder Cherilus, Leodis McKelvin, etc. But Bill identified Mayo and took him, and he has been by far the best defensive player taken in that draft. Better than Chris Long, Dorsey, Sedrick Ellis, Gholston, Rivers, etc. It makes you wonder why he doesn't trade up more because the odds heavily favor him hitting big on the guy he drafts.