Here is my feature request.
An improved search function to filter by Custom Post Type, Custom Taxonomy, Category, Tags - and all selectively. In other words, where in settings a user can specify what the search should actually index. Then display the results in AutoComplete.
Here is a feature I really like http://d7j863fr5jhrr.cloudfront.net/wp-content/uploads/search_prefilled.jpg
The idea comes from TripAdvisor. I have a similar setting where if a user wants to search for Phuket, then I would like to display my posts organised as in the image above.