It looks like Google is replacing broken Nexus 5's if you purchased it through the Play Store.
http://slickdeals.net/f/7177944-goog...play-store?v=1
I bought the phone close to the release date and had to replace it because the power button juggles. The newer batch also had larger speakers.
I was recently having GPS issues and the where the phone was frequently losing the GPS signal while driving so I might send it in for a new one.
On the Slickdeals thread people were reporting that water damaged phones, broken screens were being replaced through this program.