I'm sure there'll be a lot of talk about this trade. Stuart was a big disappointment in the Thornton trade that blew up in Boston's face and they're still suffering because of it. In general I believe it's a bad idea to pick up the top defenseman on a bad team (they account for a big percentage of the badness of the team).
Calgary needed to get their power play going so they picked up a guy who is currently running at 1.8 GF/hr on the power play and if you include goals against essentially a big 0. His defensive numbers would make anyone cringe: -4.5GA/hr and +3GF/hr, for a total of -1.5 +/- /HR. In terms of the plus scoring rate he's one of the best on the team, but a -4.5GA/hr is something to worry about (ranked 229/231).
Popular probably because of his experience, because he doesn't help teams much. He's arguably the worst forward on Boston at even strength, doesn't help much on the PK and doesn't add much to the power play. Scores about 0.25 points per game, which is below what I consider marginal (0.25). However, I believe people consider him a leader. He seems able to stay in the NHL. According to Sportsnet he is a good penalty killer (hasn't panned out this year).
He's D man #4 based on ice time, is the best defense man (statistically) on a reasonable poor PK. Signed for 4 years below market value.
Thee guys are a dime a dozen, sure he's young, but I don't think he's going to be a top line center. He's probably more valuable than Primeau though.
I see this trade as Calgary throwing away some defense for some short term offense they believe they'll need in the playoffs. They may have thrown away too much defense (as a Canuck fan I can only hope). I generally think it's bad to take a #1 defenseman from a bad team as they are likely contributing to the problems. The numbers in this trade don't make sense on the numbers side. Scouting people might be able to make sense of it. It seems strange to me that a team would want the worst statistical players from a bad team for a couple average players on a good team, that appears to be what has happened here. Looks like a bad trade on the surface, but only time will tell.