I think it depends on the site. For a portfolio, photography or a band site for example I think Flash can work but only if it's used in a subtle way and the site is not too heavy/slow. For news sites etc. where you go to get information and not to look at fancy design I think flash should always be avoided. Ok that was the politically correct answer
Actually I don't like flash at all. As soon as I see a preloader I'm out of there. I don't want things moving on a website as I find it distracting and I'll play a computer game if I want interactive animation. The web should be clean, fast and adhere to web standards.(Although it doesn't hurt if it looks pretty as well, but accessibility/ usability should be the highest priority) CSS all the way for me! (I'm going to be grilled now hehe)