iTunes 10.5.1 is now available, and with it comes iTunes Match, Apple’s cloud-based music subscription service.

For $25 a year, Match drops any track you purchase from iTunes directly into Apple’s iCloud. Songs are saved to the cloud automatically, so there’s no need to download the song from iTunes separately on each of your iDevices.

iTunes Match also takes care of songs that weren’t purchased from iTunes. The service scans all the songs in your library, and if it finds a match in the iTunes store, you don’t need to upload that song yourself — instead it uses the 256Kbps AAC DRM-free copy that Apple already has in iTunes. And if it doesn’t find a version of the song in your library, it’ll upload your version.

iTunes Match is limited to 25,000 songs, and can work with up to 10 different devices.

iTunes Match has been available exclusively for developers since late August, and was supposed to land by the end of October.

To get iTunes Match, just upgrade your iTunes version to 10.5.1, click the iTunes Match link on the iTunes Store page, and sign up using your Apple ID and your favorite credit card. Depending on the size of your collection, the initial scanning and uploading process could take a few hours.

Registration availability is currently a bit spotty as users flock to download iTunes Match, so you may get a message (like in the screenshot above) that tells you new iTunes Match subscriptions are unavailable, and to check back in an hour or two.

via GigaOM