These comments are in the order I thought of them, not particularly in order of importance.
1. You can tell it's a realistic teenage dance, because despite having a dream date, the girl still ended up crying before it was over. Ah, superfluous angst. So why on earth did it make me miss dances so much?
2. I didn't find Voldemort to be particularly scary. On the other hand, a) people 20 years younger than me are going to this movie, and they might well think he was; and b) it's a decent point that Utter Evil sometimes looks harmless.
3. The band kept playing and didn't realize anything was wrong, when Harry returned with Cedric's body. Dude. Not OK. I was in marching band, which is effectively what that group was. Someone is always watching the game, so the band can cut off fast if there's a player down. Always. Because nothing makes people hate the band like playing at the wrong time. I don't think Quidditch is different from football in that.
4. Slytherin Appreciation Society #1: Not nearly enough Snape in this film. I'll have to go get my Alan Rickman fix somewhere else.
5. Slytherin Appreciation Society #2: On the one hand, it's a shame that the actor playing Draco Malfoy has grown up too much to look right in the part. He should not be towering over Harry. On the other hand, he's growing into a mighty fine looking man. Also, the Malfoy father and son team continues to play very well off each other.
6. Related to the above, it's a shame to read excellent fanfic with in-depth but non-canonical characterizations of major characters just days before going to see something in canon.
7. I don't want to say I *like* the Dark Mark... but I think they did it very well. (I don't think it was in HP3, was it? If it was, I forgot.)
8. That pegasus-drawn carriage would make even me motion-sick. I hope that anti-nausea is one of the charms on that thing.
Nothing more at present; I may add some tomorrow after I've had a night to sleep on it.