Alright, Amazon Cloud Player and Google Music: you've met your nemesis. Alongside iCloud, Apple has announced iTunes in the Cloud at WWDC today. All your iTunes music purchases persist on Apple's end, and your devices can be configured for automatic downloads -- buy a track on one device, get it automatically on all your others (up to ten), a feature that Apple bills as an industry first. The cloud functionality is offered at no additional charge, delivering 256kbps AAC files -- but it looks like you won't be able to stream, unfortunately. That's a big relief to carriers, we're sure.
Oh, and for the music you already own -- stay, stuff you've ripped -- Apple is offering a service called iTunes Match that'll find your tracks in its existing catalog, upgrade them to 256kbps AAC (assuming that's an upgrade for you -- you might be using something lossless already), and make them available to you in the cloud. That part isn't free -- it'll run $24.99 a year. For tracks that it can't find in the catalog, you'll presumably need to use your iCloud storage.
iTunes in the Cloud is launching in beta form today on devices running iOS 4.3; no word just yet on when the final release will hit.