Egad, what an eyesore the WP devs thrust upon us with 3.8... I thought I could get used to it, but today, I found that something had broken in the css, rendering all of the back end images broken. Instead of wasting my time trying to figure out what fell apart, I thought the best course of action would be to find some way to revert to a usable interface in the first place.
wp-admin classic fit the bill perfectly. Good show!