Ebert is an idiot and should never have reviewed the movie, period. There is absolutely no excuse for the ridiculous blather he essays about a book he hasn't read, and in front of an audience that will so quickly see through it.
Saw it this morning. It is simply astounding. No spoilers, but the Ents kick butt...
I have the extended edition of the Fellowship DVD. The scale model of Isengard used for the Ents' attack on it was the size of rugby (football) field.