My wife got forced to the upgrade from Classic a while back. I kept selecting forever not to upgrade and selecting stick with Classic. Then the one day I was to check my mail, about 8 or 9 months ago, Yahoo decided not to give me a choice and force upgraded my interface to the new interface.
I do miss the old Classic View, but didnt see a way to revert back. What I really hate is how they hid the select all to delete the junk. I did find it, but its not out in the open like the Classic interface use to be for "Check All" and delete.