Assuming we got him for minimal draft capital (a 6th or so, since he's entering UFA after this season), I like the trade purely from a talent perspective. Worth noting that Mike Lombardi--most recently of the Pats, and a Belichick disciple--drafted him.
That said, I have to wonder where he fits on this team. Seems like the clear fit is at DE, which makes me wonder if a) Ninkovich and/or Sheard is more injured than we realize, or b) if Grissom and/or Flowers has underperformed in practice. Even with Ninkovich hurt and Jones traded away, I wouldn't have guessed that DE was a position the Pats were targeting to upgrade. Ninkovich (whenever he gets back), Long, Sheard, Flowers, Grissom seems like a pretty solid depth chart. Especially when McClellin can take some snaps there too. If Mingo is coming here as a DE, that almost requires a surprise cut, since it's hard to envision them carrying Ninkovich, Sheard, Long, Flowers, Grissom and Mingo.
OTOH, they could be envisioning him at LB, but to the extent that his primary strength appears to be as a pass rusher, that risks making the same mistake that the Browns made. I could see him being a LB who blitzes a ton, as Hightower and Collins currently do. Having some depth at LB with the ability to do that would be great insurance against one/both of them getting hurt again, plus it could give the team options if one of the two main guys gets priced out of their range.
Tough to say what this means, all around. My gut inclination is that the Pats are more worried about one of Ninkovich/Sheard than they're letting on. Or maybe he's just a straight upgrade over McClellin.