Yeah, because of all the RC issues, people haven't been mentioning this too much—but it's a pretty big change. Only reason to vote before 15 would be to "snipe" a spot in the curation trail, but I'd probably only do that from 9 minutes onward.
Then again I'm one of those weird people that doesn't like to autovote much. For people that autovote probably just set it at 13-15 mins. :-)