Pretty good, but plenty of room for improvemnt.
Animation was fine, graphics were fine, voice acting was fine, but the sound editing needed a little work. Like the guy below me said, the sound effects were a little bit repetative - making them seem a little less natural. When I say sound editing, I mean that the dialogue volume was a bit low, and it lacked in a few ambient sound effects.
But the biggest problem which made me give it a 3 rather than a 4 or 5 was the lack of evident story. There was a clear background: Kids have come back from a trick or treat night. The character development is fine. It takes little time for me to tell them apart. But you didn't structure the whole thing very fluently. The narrative started off ok, but there wasn't really much going on before the ending came out of no where.
The graphics and animation in this flash could have been awful but a well structured story would make up for it. It is the most important part of any flash, as it gives a significance to all that goes on within it.
You've shown that you have skill, now I want to see it put into a better concept. Therefore I wish you luck on your next project.