Apple’s (AAPL) iTunes Match service, which missed its October deadline, went live Monday morning and promptly became over-subscribed. Visitors were advised to come back in an hour. I’d give it a day or two.

The $24.99 per year service scans the music in your iTunes library and matches it to the music available on the iTunes store. Songs that don’t match are automatically uploaded.

The idea is to let you play all of your music on any of your iOS devices. It has the added value of replacing low-quality songs ripped from a CD, borrowed from a friend or just ripped off from the Internet with pristine, unprotected (i.e. DRM-free) copies from Apple’s servers.

As we noted when Steve Jobs unveiled the service last June, we can see the value for a one-year subscription, but it’s not clear why the vast majority of users would ever want to re-up. See Apple offers pirates permanent amnesty for $24.99.