I agree with Nielsen’s assertion that many flash sites overuse animation. I think that it is therefore useful to ask the following questions before using a flash ‘sting’ on a site.

1. What is the users reason for visiting the site?
2. Can we fulfill this need with a flash animation
3. Is the download longer than the length of the animation?
4. Do we want to encourage a passive or active experience of the brand
5. Is flash able to give the complexity of animation that we need for our message
6. What will be the users first experience of the site? ‘How long is this going to take to load?’ or ‘what a cool intro must be a really exciting site (brand)

Personally I feel that the long download time and the primitive (when compared to AV editing) ability of flash makes it very difficult to create a positive initial experience.
Flash is better when used for interaction, i.e. in an active experience.