Mark Berghausen of Google offered up a post last week on the Google Webmaster Central blog about the Best Uses of Flash. In it, Mark points out that Google can read the content of Flash files, but not all forms of Flash. The post provides some helpful suggestions about smart ways to use Flash as part of your web design.
My observation is that Flash is a movie. Even if Google is able to read the text in your movie, you don't decide to build a movie and then create text rich pages. The only movie I ever saw that had a lot of on screen text was Star Wars, and that was only the first minute or so of the movie. I would bet that a very small percentage of Star Wars viewers read that text in detail.
The point is that once you have decided to make a movie out of your site, you have already moved away from the premise of a search engine friendly site. That doesn't mean you shouldn't do it, but just don't expect to get much search traffic after you put it up.
Along those lines, Mark does clearly outline some ways to integrate Flash into your site so that it's a component of the site, as opposed to it being the whole site. The suggestions make a lot of sense, and can help you if you really want to have the strong visual appeal that Flash can offer on your site.