I just installed the official FlashPlayer9 from Macromedia on my FC5 box at work. I then went to the Lost and Battestar Galactica sites, two sites that previously would not work correctly with the FlashPlayer9 beta releases. Well, they work flawlessly now. Kudos to the adobe team for getting it right finally. I really think flash is a great tool, even if it isn't open source.
update: 2007-02-01
Some users may be experiencing some intermittent lockups with the new flash 9 player. Adobe has an Additional Interface Support for Linux page which provides a support library you can use in place of versions of other standard libraries you might find on your linux system. This includes OpenSSL, ICU and OSS libraries. It comes in source and you have to compile it yourself. I haven't tried this support library because I haven't had any lockups, but this info might help other readers.