Google Music beta lets you upload your music library to Google's servers and stream the content to web-connected devices like your computer or Android handset, but not iOS. Several months after launch, the service now supports iOS via a web app optimized for the iPhone, iPod touch and the iPad.
The app isn't as pretty as the native application on Android or the web app for desktops, but it's functional. You can browse your music library via artist or album. Controls are intuitive and the player is responsive, especially when you consider each track is being streamed over the Internet. Music will play in the background while you browse your online music catalog and will even continue to play when you switch to another application.
If you're a Google Music beta user, you can check out the iOS web app by pointing mobile Safari music.google.com.