The Texas State Library and Archives Commission has released Discovery Services: A White Paper for the Texas State Library & Archives Commission.
Here's an excerpt:
Discussions among libraries that have recently implemented discovery services are likely to result in agreement that implementation was challenging. However, once implemented, librarians are generally happy with their decisions to offer discovery services to their patrons. Based on librarian experiences of both the challenges and rewards of implementing a discovery service, the Texas State Library and Archives Commission (TSLAC) contracted with Amigos Library Services to write a white paper that would include basic information concerning discovery services, as well as an overview of the major discovery vendors.