Losses are narrower-than-expected loss on Thursday as it added more than 1 million subscribers during the quarter that included the holiday season.

But the results failed to excite investors who have been waiting more than a year for regulators to approve XM’s plan to be acquired by rival Sirius Satellite Radio Inc (SIRI.O: Quote, Profile, Research). The proposed deal was first announced in February 2007.

XM reported a fourth-quarter loss of $238.8 million, or 78 cents a share, compared with a loss of $263.2 million, or 90 cents a share, a year earlier.

The loss includes 25 cents a share in merger and settlement related charges, XM said. Excluding those charges, its loss was 53 cents a share, better than the average analyst expectation of 63 cents a share, according to Reuters Estimates.

U.S. regulators have yet to decide whether to approve the XM-Sirius deal. They include the Federal Communications Commission as well as the Department of Justice, which will decide if combining the two U.S. satellite radio companies would be anti-competitive, as some critics have charged.

Analysts’ opinions about the potential success of the deal have been mixed. Several have recently said they are now more optimistic, while other remain skeptical.

“Since the one-year anniversary of the deal has passed with no word from the DOJ, risk continues to exist that the deal will not happen,” Barrington Research analyst James Goss said in a client note earlier this week.

On a conference call with analysts, XM Chief Executive Nate Davis said the company does “continue to look forward to a positive resolution to this matter soon.”