While I find his stuff entertaining (I am a liberal and he is funny) I think that the NY Times referred to him as a bumper sticker masquerading as political ideology (or something similar).

Thats about right.
He raises a few good points and questions and then keeps going on for like 2 hours.

He is no John Stewart.
Stewart engages his opponents.
Moore just kind of screams in an echo chamber or chants against his opponents.
Not my favorite pundit or activist.