Well, he knew when to head for the door.
This is a bit of a classy move, imo. There's no huge call for his resignation. He could have stayed on longer. (But I seriously doubt he would have won the next election, After two majorities, he's now leading only a minority government ... though that third victory, however compromised, made him the first Ontario Liberal leader to win three straight elections in well over a century.)
The amazing thing is that he ever won anything.
McGuinty surely stood among a unique troika of charisma-challenged Canadian politicians ... him, Stephane Dion, and Joe Clark.
All sooper good guys -- but hapless beyond belief and not peeps you would expect to rise higher than Official Stenographer for the School Board Chairman.
Maybe McGuinty's decency (he had that, in spades) will win him a fond place in the memories of Ontarians.
I find I like to think so.