I am using the XML view of the quick search to get a list of issues that match a filter. If the user types in an issue number the quick search goes to the issue in a HTML view instead of the XML view i requested. If a general search term is entered the issue navigator dispalys correctly in in XML form.

This is a typical URL that i would be generating that doesn't work:
http://jira.atlassian.com/secure/QuickSearch.jspa?view=rss&decorator=none&reset=true&searchString=JRA-1

This URL works:
http://jira.atlassian.com/secure/QuickSearch.jspa?view=rss&decorator=none&reset=true&searchString=test

I am currently working around this by checking the path of the response and the content type. If it is not text/xml i request the current page again with the &view=rss parameter.