Rated 3 out of 5 stars

Confirmed: works in FF 3.5 on Mac OS X (Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; pl; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3).

This review is for a previous version of the add-on (20090922). 

Thank you for the test :)\r\nIn fact there should be no problem in most popular platforms or editions of firefox because this is only an xml and strictly comply with the rules of opensearch.