I am no website designer and not sure what you can do to improve the
SEO side of flash, in my opinion though HTML is the way to go with only small elements of flash, if you want your website to stand any chance of being ranked for your chosen keywords then "spiderable" (is that even a word?
) content is needed.
My parents don't even have flash on their PC, why restrict them as a customer when there is no need.
Maybe some of the pro's will give their opinions on this.