Adobe explained on their website:
"This will provide more relevant automatic search rankings of the millions of RIAs and other dynamic content that run in Adobe Flash Player. Moving forward, RIA developers and rich web content producers won't need to amend existing and future content to make it searchable—they can now be confident that it can be found by users around the globe."
That all sounds great, but I wouldn't go and redesign your CSS and HTML developed site for an all Flash experience just yet.
There are still many issues to consider that can prevent the search engines from treating your Flash content as regular HTML text. Back when Al Gore created the internet ;-) it started as primarily text based pages. The search engine algorithms were built around analyzing that text. And that has not changed.
Search engines may now be able to access the text within a Flash file but they cannot quite process it as they do HTML text. They still look in the HTML for important meta data used to structure the HTML. This information can include the title tag, the formatting code as in H1, bolded text and lists as well as image alt tags.
In addition to the limits of processing text in Flash, the search engines will have problems with the lack of unique URLs found in Flash sites. Many times a Flash site is all contained within the homepage URL. As you navigate through the site the URL never changes. This means all of the text processed by the search engines will have to be indexed as one single page. It also means that they may not process all of the text in the site as they will not execute all of the actions within the Flash.
The indexing of Flash text may also cause less than ideal user experiences. As the search engines find text within the Flash site not contained in the first level a visitor may discover the site in the search results only to find once they click through that the text they're searching for is not there. Rather than trying to navigate though the site to find what they're looking for they'll likely click the back button to find a page that has that info right away.
Now I'm not saying all Flash is bad. We create Flash animations on many of our web site designs. And since we are also search engine optimization company our designers typically limit the Flash portion to a small animated banner at the top of a page that has images and text. The text not being that important for search engines as we make sure the sites and pages all have plenty of unique indexable HTML text content to feed to the search engines. This type of Flash use has never been a big concern for us and still isn't. The concerns would be for those sites whose entire development was done in Flash. I'm not betting on those sites magically ranking for competitive terms suddenly.