When using a Search form (ie a form designed specifically for a query search) it would be great to be able to have a "clear" button that removes all data from the fields - so you can set the search criteria back to null.
We don't use the search as a pop-up, rather we have it displayed in a VP permanently so it is more of a filter and can be used again to filter further. Currently to clear it you have to manually delete all the stuff you have typed in the fields. With a button it would just clear it in one press.