When a team wins a Stanley Cup, and that team was the product of a multi-year construction effort by the general manager, it's pretty clear what his grade should be.
Chiarelli got the big decisions right on this team: he built the core of the team around Zdeno Chara, Patrice Bergeron, David Krejci, Milan Lucic and his goaltending. He stole Nathan Horton and Gregory Campbell from Florida shortly after the end of the 2009-10 season, and Horton became a core player while Campbell was one of the best fourth line centers in the NHL. He added Chris Kelly, Rich Peverley and Tomas Kaberle in-season, all of whom helped the team in the playoffs. He dumped Marco Sturm's contract, creating cap flexibility the team needed. He held onto Tim Thomas when many (myself included) called for him to deal his goaltender for another scorer. He stuck by Claude Julien when fans demanded Claude's head on a pike. And he didn't strip-mine his minor league system or fritter away his cap flexibility to win a Cup, setting Boston up for potential long-term success. And of course, long-term success is the best kind.
Since 2008, Chiarelli has drafted well in Boston, and has done a good job stockpiling draft picks and turning picks into players and back again, with most of his trades proving to be net gainers for the organization. Hockey Prospectus recently ranked Boston's minor league organization 7th in the NHL, and the Bruins have multiple prospects who should be ready to contribute over the next four years, and keep the flow of low-priced, high-performance talent flowing to the pros. It is too early to judge the 2010 draft, of course, but early returns (i.e. Tyler Seguin) are positive.
Not every Chiarelli deal carried the Midas touch; he overpaid for Kaberle, and gave up on Blake Wheeler too soon. The Phil Kessel deal was not the product of a desire to trade his young star, but rather, was an unfortunate by product of his tendency to overpay secondary players and not leave enough money for important ones. Happily, Chiarelli seems to have learned from this mistake, as evidenced by his decision to conserve cap room for the coming long-term contracts for his #1 line.
If Chiarelli has made a few missteps along the way, his good moves far outnumber bad ones, and his work in 2010-11 helped bring Boston a Stanley Cup.