Hi,
re: the new email authentication in 1.5: I assume it will be necessary for a user to authenticate themselves on every wiki on which they have an account to use email features on that wiki. For Wikimedia, where many people have accounts on a dozen wikis or more, that might be a major PITA. I would suggest disabling this until we have single login -- unless someone is willing to hack it so that a single authentication will take effect for all wikis.
Best,
Erik