I've been playing with the Search API and I can add new Facet Displays and filters, but no matter what I try I can't get any fields other than Price, Latest and Title to appear as Sort options. What's the 'trick'?
For other travelers, the answer is that it's a bug with a patch that has not been made part of the official distribution as of 26 Sep 2014. See #6 for the patch.
