I used to read Ebert a lot while he was still alive. It's not that I necessarily agreed with him all the time - I find that he both overrates some well-made children's movies, and falls into that typical critic's cliche of thinking the values of his generation are universal (more on that in a second) - but rather that I appreciated his sense of film history. To anyone looking to really get into 20th century cinema, Ebert's list of 'The Great Movies' would be a fine entry point.
That being said, we should recognize that, though Ebert is probably the most famous movie critic of all time, he's hardly considered a great one by his contemporaries (despite the Pulitzer). For example, I have a compendium of American film criticism: Ebert gets a couple pages out of 400 or so. I never really thought about reading the first version of this book (I Hate...Hated This Movie) however I found this one for a dollar, so i read it.
On the whole, it is very entertaining. If you enjoy Ebert's reviews, then you will enjoy these. I find Ebert's criticisms of the way films fail to be very instructive when thinking about how I express myself about movies, and in thinking about movies in general.
But, as usual, Ebert has some real surprise reviews. Two films in particular he hated which I really liked. (One of which would be on my short list for best movies of the 2000s.) Sometimes, Ebert seems morally opposed to a film, rather than critical of the film as a film. And those are the times I cannot agree with him, nor even take him seriously. Sometimes he sounds like a cantankerous old mad, railing against the moral failings of kids today. And unfortunately it's those reviews that make this book a bit of a disappointment.