Once you've downloaded and installed iTunes 10.5.1 (required), you can use the iTunes Match tools to get started. It scans your entire library to find the songs that it already owns and sells via iTunes. These songs are automatically added to your iTunes Match account, which costs $24.95 per year. If you have songs that are not available from iTunes, Apple will then upload the rest of your library, which will also be available from iTunes Match once the upload is complete.
With iTunes Match, you can use multiple computers and multiple iOS devices. For example, I set up iTunes Match on three computers and three iOS devices. It only takes a few clicks to get each separate device set up. There appears to be a limit of 10 devices in total that can be mated to a single iTunes ID / iTunes Match account. If you activate iTunes Match on an iOS device, be warned: It deletes all the locally stored music and replaces it with your iTunes Match library. Be sure to sync up your devices so you don't lose any locally purchased music.
[Before you hit the App Store, check out 10 Innovative iOS 5 Apps.]
I have a large music library with nearly 20,000 songs. It took iTunes Match a total of six hours to scan my library, match it to existing iTunes content, and then upload the rest. Once this step was complete, setting up iTunes Match on the other devices took less than one minute each.
(By way of comparison, it took Google Music three and a half days to upload my entire music library. Amazon's Cloud Drive was slightly faster at 36 hours to upload my entire library.)
For the most part, iTunes Match works with few headaches. I was able to access and stream my entire catalog of music from all devices easily. It streams music over the Internet to your computer, but needs to download and store music on iOS devices locally (playback starts long before the song is fully downloaded, which works over both Wi-Fi and 3G). Music is streamed back at whatever bitrate it is encoded with. Songs that Apple owns are streamed at 256 Kbps.
Sound quality was very good. I could not tell the difference between local tracks and those streamed from Apple's servers.
The service isn't perfect, though. It duplicated my playlists across all devices -- meaning each playlist is represented twice on all my devices. This is a bit of a headache that will take time for me to clean up. iTunes also didn't match all the songs that I know are available from iTunes to those in my library. For example, I own all the CDs from a European progressive rock band called the Flower Kings. I purchased these as CDs and ripped them myself. Even though Apple offers these same albums in iTunes, it didn't match them to mine. Why does this matter? Because iTunes Match uploaded the files unnecessarily, and I won't have access to the higher bitrate copies that iTunes owns. Not the biggest problem in the word, but grating just the same.
The bottom line: iTunes Match does what Apple advertises and provides streamed access to your entire music library.
But what about Google Music and Amazon Cloud Drive?
I've uploaded my entire library to both services. I paid Google and Amazon each about $20 for the 140 GB of storage space needed for my music catalog, making the $24.95 yearly cost of iTunes Match negligible in my book. iTunes uploaded faster, but probably only because it already owns a large chunk of my library and Google and Amazon each had to upload more files. (iTunes Match and Google will automatically update as you purchase new music. Amazon only does this with tracks purchased through Amazon.)
The real issue, however, is accessibility.
iTunes Match is available from iTunes on a PC, or from the iPhone, iPad, and iPod Touch. It only works in the iPod music player on the portable device. You need network access to reach your entire library, but iTunes Match will cache playlists for offline playback. iTunes Match will not work on an Android smartphone, or on Windows Phones, BlackBerrys, Android tablets, etc. iTunes only matches music files and music videos, not movies or podcasts.
Amazon Cloud Drive is available on Android smartphones and tablets via the Amazon MP3 Store application. It offers full access to your entire catalog of music, and will also cache locally for offline use. iOS device users can access Cloud Drive files through the Safari browser, but the experience is frustrating. It is slow, the controls are difficult to use, and playback can be stuttery.
Google Music is available on Android smartphones and tablets via a beta application. The application works quite well and streams your music over 3G, 4G, or Wi-Fi for playback. Google has not created an application for iOS devices, but it offers an HTML5 Web app that can be used on the iPad to access and playback music files. The Google Music Web app as used in Safari is a much better app than what Amazon offers through Safari. Google lets you upload tons of different file formats to your Google account, but not all are accessible through Google Music (i.e., you can't stream movies).
I've been unable to get Amazon Cloud Drive and Google Music to work at all on mobile platforms other than Android and iOS.
Is there a clear winner among these three? I can't say that there is. Each has its own strengths and weaknesses. For Android users, Google Music does make more sense (and may make even more sense depending on what Google announces), as does iTunes Match for those invested in Apple's hardware.
Whichever you choose, the cost to store and access up to 25,000 of your songs over the Internet is cheap as far as I am concerned.