I'm surprised this threaded faded away since the movie came out.
I just got around to seeing it, and thought it was fantastic. I'm sure Alan Moore could come up with a hundred legitimate reasons why it was awful, but I can't. Maybe it's because I was younger and dopier when I read the book (I resisted the temptation to read it again before seeing the movie), but the characters really jumped out for me in the movie and gave me a better appreciation for the book.
Was it financially successful? I could see how the studio would expect it to be based on the success of Heroes and Dark Night, but I could also see how audiences wouldn't like it based on the darkness, unfamiliar characters, and complete moral uncertainty. I think audiences are more sophisticated than most do, but when you see a superhero movie you go in with certain expectations that Watchmen doesn't fulfill.
Overall, I'm with Ebert. Four stars.