I've always been a casual fan of Star Wars. By casual, I mean that I don't dress like a wookie and wait outside the movie theatre a week before the movie starts showing. I enjoyed the dark nature of this movie which has been absent from other versions.
The main plot of Star Wars has always revolved around Anakin/Vader, whos actions effect the fate of the universe. The prequal movies are supposed to show how this one nobody becomes the most significant person in the universe. This rise to significance, however, is down the path of evil, and needs to be told in a dark and depressing way. The fundemental problem with Episodes 1 and 2 is that there was such a light-hearted mood in the movies that they did little to advance this main plot. Episode 3 was the first time that a Star Wars movie has showcased powerful emotions, in my opinion. Although the movie was sometimes corny, it truly was powerful in scope. Then again, Titanic was corny and it was the highest selling movie of all time.
So basically, I really enjoyed the movie. I urge even moderate Star Wars fans to go out and see it.