There's no stopping it now: the marriage of XM and Sirius has been cleared by the Federal Communications Commission (FCC), under a few conditions. The deal is said to offer subscribers better choice in the channels they listen to by the two companies and the FCC, but its criticizers see it as anticompetitive, taking the two major Satellite Radio providers and making them one mega company. While the FCC admits this in their press release, they also say that the new conditions make the deal fair and in the public interest.
Among the highlights of the conditions the two companies face in their merger are a 3-year price cap (to be reviewed 6 months prior to its expiry), a requirement to offer customers new programming packages within three months of the merger taking place, and a mandatory application to extend the service into Puerto Rico, also within 3 months.
Much more information is available directly from the FCC.