Monkette and I saw Shrek the Third on Saturday and unfortunately the majority of the critics are correct -- it just doesn't match up with the first two.
The problems are easy to identify: pace and tone. The movie starts off without any real funny bits, a rather overdrawn death scene for the frog-king of Far Far Away and without any good action/humor scenes until midway through. The best set pieces (the high school where Shrek finds Artie and the attack of the killer princesses) come too far into the movie to regain the momentum squandered at the beginning.
And that's too bad because there is some good stuff in here (including the concluding domestic scenes with Shrek and Fiona, and the new age goofiness of the wizard Merlin [voiced by another Monty Python alum, Eric Idle]) but it's not enough to make the movie anywhere near as enjoyable as the others. Then again, considering the reviews for the other sequels currently on screen (Pirates 3, Spidey 3), is seems three is a tragic number for this summer.
The Monk hopes that the last #3 and a #5 can restore some luster to what should have been a bang-up movie season. Given the trailer, Monkette and I have high hopes for Harry Potter 5; given the predecessors, we have similar high hopes for The Bourne Ultimatum.