Worldcat Identities went into production as part of Worldcat.org over the weekend. It is currently linked to from under the 'details' tab. We will be interested to see how it is used and review other integration options over time.
One nice feature is that the Tag Cloud (these are FAST headings derived from Library of Congress Subject Headings in the records) sends searches back into Worldcat.
Thom discusses the implementation over on Outgoing.