This is definitely worth updating, if only for the security fixes:
You might want to uninstall Flash Player v9 first.
Alas, still no support for 64-bit browsers. Adobe says they’re “working on Flash Player support for 64-bit platforms” and will deliver it in “an upcoming release of Flash Player following Flash Player 10.”
Flash Player 10 works with IE 6/7 (and IE8 Beta 2, I can confirm), as well as Firefox 2 and 3, on all Windows versions. AOL 9 and Safari 3 are supported on desktop platforms but not on Windows Server 2003. Opera users, you’re OK if you use XP or Windows 2000 but
apparently out of luck not officially supported if you use Vista or any Windows Server edition.
Update: In the comments, Danny notes that he has installed Flash Player 10 on a system running Opera 9.60 and Vista Ultimate SP1 and it works just fine. Thanks, Danny!
Update 2: Ars Technica has run some performance tests:
As the numbers will show, Flash performs far better in Vista versus Mac OS X running on the same hardware, and it actually improved slightly with the version 10 update.