Slacker Radio’s February website overhaul really paid off, resulting in millions of new fans and mobile downloads in less than three months.

Since launching its completely redesigned digital music service on Feb. 13, Slacker picked up more than 6 million new listeners, 3.5 million of whom are listening via mobile devices.

Slacker’s makeover provided the site with a fresh new face, as well as simplified navigation and a new “Music Guide” with industry news and videos. Slacker also replaced the Home, Now Playing, Create Your Own, and Devices buttons with a panel interface and large icons.

“We’re thrilled with the results of our relaunch,” CEO Jim Cady said in a statement. “Since mid-February millions of new people are tuning into Slacker, they’re spending more time listening, and our paid subscriber base is growing fast.”

The result, Slacker said, is “the most complete music service on Earth,” with streaming radio and on-demand access to more than 13 million songs (and growing), plus news, sports, and talk radio from ABC and ESPN.

Music fans can tap into Slacker Radio from the Web, every major smartphone platform, in cars, and via smart TVs and gaming consoles — most recently the Xbox 360. U.S. and Canadian Xbox Live subscribers can now rock out to their favorite tunes through the Xbox Live Marketplace. Those with the Kinect sensor can also use voice controls.

Users can create their own stations or explore the hundreds already available. The service comes in three flavors: free streaming; commercial-free access with unlimited song skips for $3.99 per month; and the addition of offline listening and on-demand access for $9.99 per month.

Slacker is available for free in the Apple iTunes Store(Opens in a new window), Google Play(Opens in a new window), Windows Phone marketplace(Opens in a new window), and BlackBerry World(Opens in a new window).

For more, see PCMag’s review of Slacker Radio (slideshow above), as well as Slacker for Android and Slacker for iPad. Also check out Spotify, Slacker, or Pandora: Which Streaming Music Service is Right for You?