Having experimental features available to developers creates pressure for all browsers to move forward. Without that we won't know what is important to developers because they'll be stuck using what the browser maker's deign to make "official".
Just playing devil's advocate here ...
The 'yay no vendor prefixes!' crew seem to have very short memories on what it was like before vendor prefixes..IE Waiting a LONG time (years) for a CSS feature to be 'recommended' by the w3c.
Vendor Prefixes were the best of a bad situation, I think they will be missed quite quickly.
I'm all up for this movement, but the W3C will need to move a lot quicker if this is to happen. Otherwise innovation will just grind to a halt again like it did before.