I love iTunes Match: part media streaming, cloud-based, music hosting service and part music amnesty program I think it has a lot to offer that it's rivals don't. It's headline feature is the process by which it scans your music, determines what you have and where possible 'gives' you the 256bit AAC iTunes version - in a sense legitimising your music from whatever source, with the music companies getting a cut of your subscription fee where otherwise they get nothing. It's a pretty good situation, it's affordable and offers a real benefit to you as a customer.
You can also stream your music to any Mac, iOS device and, critically for some, Apple TV. It blows the equivalent Amazon and Google offerings out of the water in my opinion on this basis alone, and importantly does not contribute to your iCloud storage limit.
The other really cool thing it has is Genius support. I'm a huge fan of Genius Mixes and Genius Playlists; neither I use on a daily basis but both I have been glad to have on numerous occasions. I hate setting up playlists manually, and generally do not want to just listen to a random shuffle.
The one feature I do use of iTunes that isn't supported is Smart Playlists. These are playlists that obey simple logical rules to build a dynamic track list. I only have a few, such as one for music that I haven't rated yet, one for music I love but haven't listened to in a long time. These currently don't sync (though standard playlists do I believe. For this reason, my iPhone (the device I use for music 90% of the time) doesn't capitalise on iTunes Match as all my other devices do. Instead I still wirelessly sync music to my iPhone every night when it charges. This isn't really an issue at all, but it would be nice to have the iTunes Match support.