are there any examples of functioning OpenSearch interfaces to library
catalogs or library information systems?

I'm specifically interested in those that not only advertise a text/html
interface to their catalog, but who include OpenSearch response elements.
One example I've found is Evergreen; though it's not clear to what extent
this interface is used or implemented. For instance, their demo
installation's OpenSearch description advertises an ATOM feed, but what's
returned doesn't validate. (*)

Are there other examples deployed (and does anybody know applications that
consume OpenSearch feeds?)

 - Godmar

(*) See, for instance:
which is not a valid ATOM feed: