I’m currently in a project using Search Server 2008 and let me tell you it has been a very goos suprise.
Having experience with the search of Sharepoint (2003 / 2007) the use of Search Server 2008 it is quite smooth, most of the functionalities are the same that the Search of MOSS provides, you can have has content source Sharepoint Sites, Web Sites, Public Folders and Public Exchange Folders. All this information can be indexed, you can define metadata, scopes, crawl rules, set schedules for incremental and full crawls.
Well, there is even a Express version for us to play with.
It is a real alternative to organizations that just want to have their existing information searchable.