Strong single action grip, no roll feel coming through the ball. If he rolled the arms aggressively he'd be big time fore left.
I use a similar swing. The feel for me is that I'm hitting the ball with my left wrist bone, so that I don't over roll into impact.
It's basically angled hinge swinging, Jack, Duval, played in a similar way.
Freddie explains this a bit on this clip
[media]http://www.youtube.com/watch?v=mgdgwonPRIE&feature=related[/media]
But man what great tempo!
Cheers
Steve