If I request from the /questions route (for example,) I get a list of questions and some relative route data. What I don't get is a nice, neat, full URL to the question on the site:
site_url: http://stackoverflow.com/questions/3159491/problems-with-javascript-and-hcommandlink
I can imagine lots of cases where you'd want to be able to link a question or answer represented in an app to the site where it was posted. I can build the URL above from the return data fairly easily, and I'm fairly certain the routes on the SE sites won't change, however...
It would be nice to get the site URL directly from the API. In the unlikely event of a change to the SE routing, the API could report the change seamlessly and apps just continue to link to the sites without modification.