At XM, Boldly Going The leading satellite radio service, with more than 500 employees and 2.5 million subscribers, has now come into its own and competition is sizzling.&lt;FONT face="verdana,MS Sans Serif,arial,helvetica" size="-2" color="#666666"&gt;&lt;B&gt;-The Washington Post&lt;/b&gt;&lt;/font&gt;