I liked Ebert, and usually agreed with his reviews. I did find that his "3 1/2 star" reviews (out of 4) tended to be more reliable than his four-star ones, as he did tend to have some odd picks for four star movies.
He was unpretentious and did not come off as a film snob. When you read his reviews, you felt like you were hearing from a common (though intelligent) man who was giving his honest opinion of whether he enjoyed the film or not. He wasn't obsessed with the artistic merit of films. If he liked watching a movie, he gave it a good review.
I also respected him for his lack of bias. For example, Ebert was not a Republican, but he was quick to criticize the common Hollywood practice of making Republicans (or implied Republicans) the bad guys.