We told you last week about the new music service from Research In Motion. Thursday, the cloud-based service launched. You pay $5 a month for 50 songs you can stream or download right to your BlackBerry device, and you can trade your songs for up to 25 songs in their library every month.

From Ars Technica:

“Although the songs from BBM Music are treated like a subscription (that is, they disappear when you cancel the service), they can still be cached to an SD card for offline listening. This is not unlike Spotify’s own offline mode for Premium subscribers, though a Spotify Premium account costs twice as much per month (at $9.99) than BBM Music currently costs. Then again, Spotify (at any tier) lets you listen to more music at a time than BBM Music, so there is certainly a feature trade-off.”