This film introduced unexpected humor which meshed well with the darkness of the rest of the plot.
As usual, the movie could not contain the book. However, I think less time could have been spent focusing on the budding teenage romances, and more on the complex plots that carry into the next book/movies. Cutting down on some of the teen flirting and "snogging" would have left precious minutes where important scenes involving the memories of Voldermort and Dumbledore's mission for Harry could have been expanded.
Teenage focus aside, I found the movie to be excellent. The visual effects were astounding and I also appreciated Dumbledore's last act of magic in the film, which showed his tremendous power and grace one last time.