Apple's cloud music subscription service iTunes Match has gone live – for Americans only, at first.

Announced in June, the $24.99 service allows subscribers to stream their music collections back from Apple's servers. Unlike other "locker" music services, Apple scans your iTunes library so that much, if not most, of your music does not need to be uploaded first. Hence the name.

It's a sort of locker and sort of a backup service then. There's little more to it than that.

Apple did successfully negotiate with music rights holders who gave it their blessing. Other locker services have either forgotten to do that or assumed they didn't need to – racking up lawyers fees on both sides.

One serious drawback has been reported: the service erases the music on your iPod or iPhone so the Apple-server version becomes the canonical library.

"The service is supposed to take the hassle out of transferring files onto multiple devices, but at the moment it only causes bigger headaches thanks to long set-up times and clumsy song management," notes PC World.

Arch-rival Google, which spends more time lobbying about copyright than creating new and interesting music services – and is falling behind as a consequence – looks set to unveil its own offering in Hollywood tomorrow night. ®

Updated to Add

According to Macworld.com testing, the Match warning stating "iTunes Match will replace the music library on this device" is "a big fat lie" and in fact music previously sync'd usually remains on the device: but not always. According to Macworld "if you turn off iTunes Match and then sync a few random tracks that aren’t part of your master library, those songs will vanish after you turn iTunes Match back on."