People who use experimental functions already know that a standard, cross browser behaviour should not be expected at all.
In my opinion there is no need to prefix new features. It makes it harder to use them as you have to write the standard property, chrome's prefixed property, firefox, opera... it also makes stylesheets bigger (who is going to delete all those prefixed properties in the future, when they are not needed anymore?).
I don't see any advantages, but it is just my opinion.
