If you plan on using flash for your web site, there are trade-offs in doing so. On on one hand, it can make your site dynamic and solicit interaction from the user. It is also a creative way of presenting information that would look elegant and rich. And being advanced this way, can be a positive feedback from the visitor.
Though, much has not been said about using flash for web sites. The main point being, the inability to use seo techniques for flash content. That way, you cannot employ useful techniques to make your page rank higher. If that happens, then there would be less visitors who can appreciate your web page thus defeating the purpose of implementing flash in the first place.