One, in previous versions, link uniqueness was based on the tuple (context IRI, link relation, target IRI). In the current version, this is expanded to include all target attributes.
Two, previous versions of the Link draft did not adequately address the use of the Link header field's anchor attribute and the determination of the Context IRI. In the current draft, the Context IRI is resolved in accordance to Section 5.2 of RFC 5988. This allows the anchor attribute to be used to override the default context IRI.
This draft also deals with ambiguities in IRI comparison, 2xx response codes and conditional requests (well, I added the parts about condition requests in the previous iteration but had not specifically called those out as a change yet).
As always, feedback is requested and very welcomed.