Windows Search 4.0 will begin automatic updates using Windows Update within the next week or so to Windows Vista, but will be an optional update for Windows XP users.
The new version will update the indexes, Search will release most of the requested resources and slow down the indexing process as soon as it detects mouse or keyboard activity, or when another application requires computer resources.
Details of the update are posted on TechNet at Reminder - Windows Search 4 coming to WU soon...
The opportunities for ISVs is to integrate Search with the data in your application. This includes Windows Search, Search Server 2008 Express, Search Server 2008, and Office SharePoint Server 2007 using the Search Server SDK.
For more information about how to integrate your application with Search, see Enterprise Search Resources for Developers.For more information about the free version of Search Server, see Search Server 2008 Express.