Apple launched their iTunes Match service in the US back on November 14 and I signed up shortly thereafter. I've read some mixed reviews since then, some of which have been pretty negative, but my experience has been very positive so I thought I'd put up a post with my experience using the service for the past few months. If you don't feel like writing the whole piece, I'll sum it up by saying that this is a service I've wanted for years and am very happy that it finally exists.
For anyone not familiar with the iTunes Match service, the idea is that for $25 a year you can have iTunes scan through your music library on up to 10 devices. Using technology that has not been publicly discussed in any detail by Apple but presumably involves using Fourier transforms, iTunes looks through your music library to identify any songs that are already available from the iTunes Music Store. For all of those tracks, iTunes will make a note that you have the song and are entitled to access it. For any tracks that don't match against the iTunes Music Store it uploads your local copy of the song to iCloud.
The magic is that once this process has completed, all the songs in the library (up to 25,000 tracks) are available on up to 10 PCs or Macs running iTunes or iOS devices (iPhones, iPads, iPod touches) where you have signed in with your iCloud account. When a new song is imported it will automatically be added to the iTunes Match library either by being matched against the iTunes Music Store or uploaded if the song is not matched.
All of the iTunes playlists are also synced across devices and changes made to a playlist on one device are instantly propagated to all your other devices that have iTunes Match turned on.
The service is not all things for all people and depending on your mix of devices this may be more or less useful. For me it's great. My primary iTunes library is on a Windows PC and it contains somewhere around 10,000 songs.
I currently have an iPhone 4 and have been an iPhone user since the 3G came out, but I have never been very good about syncing music to it. Even with the highest capacity iPhone there's no way I can have all my tracks synced to the phone so I have to make choices about which songs or playlists I want to sync. And invariably I'll be somewhere away from my computer and want to listen to something I haven't thought to sync. Plus I tend not to plug my phone into my computer all that often and actually I don't even bother turning that Windows PC on much. So mostly I don't listen to my iTunes library at all any more. Pretty sad.
I also have a 17" MacBook Pro but I've never bothered to copy my library to this laptop because, while it could hold the entire library, I don't necessarily want to commit that much disk space to music since I already have it on my home PC. So I don't listen to music in iTunes on my laptop either.
That's been a lot of music just sitting there not getting enjoyed. Too bad.
Since Spotify launched in the US over the summer I've been subscribing to Spotify Premium and doing most of my music listening through Spotify. I love Spotify and they have an incredible selection of music, but they don't have everything that I have in my iTunes library. I don't really buy music much any more since I can listen to most of what I want on Spotify or YouTube, but when I was in my teens and early 20's I bought a LOT of CDs, including a fair amount of obscure stuff that just isn't going to be in Spotify and may or may not be in the iTunes Music Store.
With iTunes Match I now have access to my entire library on my iPhone 4 as well as my MacBook Pro and I can choose to download only what I want to listen to. But I can make that choice spontaneously as I think of something I'd like to hear. I've read some critiques of the service that state that you can't sync everything at once, but that's actually not true. If I open my iTunes library on my MacBook Pro and select everything I can indeed right click and download everything. That would probably take a while. However I have used that technique to download everything by certain artists to my MacBook Pro.
The one feature that would be nice is if there were a web based player on iCloud.com that would let me listen to music streaming through a browser if I happen to be on a computer that doesn't have iTunes or that I can't link to my iCloud account for some reason. But that's a "nice to have" feature request and not a use case whose lack of availability I've actually wanted to use in any real life scenario as yet.
I'll confess that I'm still mostly listening to music through Spotify but I suspect that I will find myself listening to more music in iTunes now that I have my library accessible wherever and whenever I want it. Definitely worth $25 a year.