Spotify is really popular in Europe, offering a huge library of music to listen to on demand from computers and smart phones. I’ve said before that I’m not a huge fan, and MP3tunes addresses on of my complaints: that Spotify doesn’t have everything I want to listen to.
I have everything I want to listen to, though, and MP3tunes allows me to upload my music to their service, and then stream it from any browser, or my iPhone (there’s even an Android app, if you have one of those). The browser service best, but the iPhone app seems to be unstable. This may be due to iOS4, so hopefully they’ll fix it soon.
MP3tunes is an interesting service, but I’m still not a big streaming fan. I will stream things, but I don’t see it as the ultimate solution. I’ll keep storing things locally, as it saves energy and bandwidth on my phone. For me, the best things about the web and music are the sharing possibilities. Spotify’s playlists are an excellent example, and SoundCloud, which allows you to upload music and share it, is a great place to discover new music.