I just finished Watchmen yesterday. It was the first graphic novel I've ever read, and it certainly made me appreciate the medium. I was unsure at first, but they really did some great things with the dialogue/artwork combinations.
The actual story, too, is rather great. The characters are obviously the most important part, and they're amazing. The narrative got a little strange by the end, but considering the contents of the rest of the book, I don't think it was impossible. I was a little disappointed at first, but I think I'm growing to love the conclusion (and the rest).