WordPress 3.8 was released yesterday (December 12, 2013) with a big interface change. Apparently there are no known issues at this time and alot of my designer friends are not seeing any conflects, but I suggest waiting at least a week or two and seeing what others are saying on Twitter and Facebook before updating on your site. I myself will wait at least 2 weeks before I update. I like to be careful!
Read about the new changes here: WordPress Blog