In System Preferences and in Sharing & Permissions (under Get Info), when clicking on the little lock icon to make changes, it either does nothing or opens and then closes. It never gets to the point of requesting authentication.
While the OS is blazing fast (most apps bounce once in the dock before being fully functional), I've noticed quirks that makes you wonder how they made it into the final build.
I'm looking forward to 1.6.0.1 which can't be more than a week away at the rate that bugs are being found.
This is a FONT issue, same one I was having above.
Use font book and get rid of all the duplicate fonts, because the lock not opening is a font crashing the authentication window (securityagent) which asks for your password.
Likely you got a bunch of windows on first run telling you about some .dfont duplicates with the same name as a system font.
I'd try:
Use fontbook.app and trash all the system font duplicates with (.dfont) -- log out and when you come back the authentication window should work.
Not how I fixed it, since after 10 boots trying to fix it I finally got the windows again and let the OS trash the .dfont files.