I saw this movie last week.
Overall I thought it was a decent conclusion to the trilogy; much better than the second movie. However, the first film is still by far my favorite in the series.
Pirates 2 and 3 suffer from the Matrix syndrome - that is, they essentially split one story into two movies, and unfortunately many of the jokes from the first film were rehashed in the second film (and to a lesser extent in the third film). Thankfully, there's enough new moments to keep this film more interesting than the second movie, but I can't help but feel that it would have been more focused if they've made each of the three movies separately, or just made two movies.
Like Daz said, the brethren council scene was well done, and I liked the way this movie portrayed most of the pirates. Unfortunately, while some of the ?baddies? from the first film have teamed up with the heroes, they've been replaced by a new set of villains. It would have been more interesting if we were given reasons to sympathize with both sides of the battlefield. In the end, it still felt like there were two "sides", heroes and villains.
I cringed when I watched Norrington's death scene. It would have been much more interesting if he had switched sides more than five seconds before his (predictable) death.
I liked the ending - it wasn't predictively happy. Although I think it would have preferred not to have seen the epilogue the epilogue that came after the ending - it would have been better to leave that part to imagination.
I recommend this movie, and if you enjoyed the other movies in the series, it's more of the same style, and wraps up most of the loose ends in the second film. But in saying that, I'm glad they haven't set it up for a sequel. Even Jack Sparrow got a little tiresome in this movie, and after seeing it, I'm convinced that the series has run its course.
At the end of the day, Pirates of the Caribbean: At World's End, like the first two movies, doesn't take itself too seriously, and because of this, it works quite well. It would have failed if it had tried to take itself more seriously. It is what it is - a fun movie, nothing more, even if it tries to be "The Return of the King" of this series.
One last thing, At World's End has the best soundtrack in the series. Definitely worth listening to if you like powerful theme music in films. Check out this YouTube video for an example - http://www.youtube.com/watch?v=ySPrhAKAbdw) - between 2:21 - 4:10. Note, the pictures in the video aren't from Pirates 3, just the music.