To some extent, you can ameliorate these concerns, but using Flash for a website generally leads to usability issues.

Here's an article from me explaining why, if you're interested.

http://informationrain.com/2007/07/25/why-i-dont-make-flash-...

In my opinion, flash should mainly be used for what it's great at....making games, some types of interactive tools, and a decent quality cross-platform video solution.