Having seen it again last WeRAB it really struck me just how effective the contrast between the trio and Draco was. On the one hand, you had three teenagers whose (Harry aside, obv) main strife in the film was romantic, having to deal with typically teenage worries. On the other, you had Draco, same age, same schooling etc having to deal with being practically forced into murder. I haven't explained it well, but I hope its clear...
I also liked the contrast between Harry and Draco's duel in this film compared to the one from Chamber of Secrets. No more tickling hexes, it was aiming to hurt properly. Shows how the characters have changed and developed and grown up in just a few short years.