I'm not a Pats fan, but this is a great pick for those of you who are. I watched a fair bit of Mallett in college. He filled in really well as a freshman at Michigan when Henne got hurt for a few games, then got screwed over when there was a coaching change and they wanted a running qb (which certainly doesn't describe Mallett.) There weren't many reports of behavior issues during his freshman year at Michigan -- they largely started to pop up when/after he transferred to Arkansas. When he was at Michigan, I was really excited about him. I don't remember a qb who looked better as a freshman than he did. He threw beautiful deep balls to Mario Manningham seemingly every game. If Lloyd Carr hadn't retired, Mallett probably would have been the best qb in Michigan history, no offense to Tom Brady (or Elvis Grbac, who's still my #1.)
At Arkansas, he started to put some better touch on his short passes. Aside from his rumored attitude issues, which I'm willing to bet Belichek can fix, his biggest area work is with his footwork. Once he moves in the pocket, he doesn't get reset, and then tries to throw with only his arm, and his accuracy suffers. I also didn't find him to be the most convincing using the playaction (which Petrino called for almost every dropback.) He also had real trouble with the center exchange at Michigan. Some of that was because Michigan's starting center got hurt that year too, and was thus on the center, but some had to be on Mallett. I didn't notice that problem continuing at Arkansas, so that looks like something he's fixed.
My expectations for Mallett are to start the year as third-string, but to take over the #2 qb spot before the season is over, and then be #2 for certain in 2012. (Depending how long the lockout lasts, however, he might be #3 all year because Hoyer has enough of a headstart with the offense.) Of course you don't want Brady to get hurt, but you'll soon have a backup qb who can win games, instead of not lose them. Depending how long Brady keeps playing, Mallett may be able to take over and be your long-term starter after he goes, or maybe he'll leave in FA/be traded before that happens. I don't think you'll see Belichek take another qb in the draft as long as Mallett and Brady are both here.