Today was Apple's announcement of its cloud music system. It was a pretty major one and it offered one feature that neither Google or Amazon have, the ability to scan and match any song in a user's library. This was originally a feature that mp3.com offered and was the reason they were sued out of existence. Apple negotiated very carefully to get the rights and the payoff is big. Instead of storing the user's files they are just serving a copy from their own database.
The downside is that it seems to be device based so you can't really access it without an iOS device or computer with iTunes. Its also limited to songs that are recognized by iTunes. For Apple users its pretty much a no-brainer but for everyone else there needs to be a good reason to justify using it. Here are two possible reasons.
1.) Fixing Old Rips
I'm probably not alone in having old CD rips of less than stellar bitrate. I didn't really care at the time because PC sound wasn't all that great to begin with. Apple's matching service offers a very nice upgrade in sound quality for only $25 (although limited to 25K songs) and far less work than digging out a box of CDs and manually re-ripping. It'll still be time consuming but much less so.
2.) Laundering Music/Getting Around the Rumored Google Cloud "Authenticity Check"
Since the Google Music Beta started there's been rumors illegitimately obtained music might get flagged and removed if uploaded. One way to avoid that would be to obtain "clean" copies from Apple first, assuming there is no similar check being performed by Apple. To be safe, it would be a good idea to remove any suspicious looking comments from files using program such a Media Monkey before any uploading takes place. I'm not recommending that anyone do this, but with the way Apple has structured their offer it seems to be essentially an offer of amnesty from the four major labels and for the price quite an affordable one at that.
Apple's Match service won't launch until some time in Fall so the details may change and Amazon and Google may still catch up.