It took me a while to solve the conundrum. The problem was that the Google Music player for Android doesn't directly handle WMA files. While the music player built into the Xoom is the standard Android player, the player in the Droid X was tweaked by Motorola to give it the capability of playing WMA files. So even though Google Music can stream WMA files, and the Music player can play that stream, the normal Music app can't play WMA files when they're locally stored. So the Droid X can play them; the Xoom can't.
Google would do well to fix this by giving the normal Android Music app the ability to play local WMA files, because otherwise it's quite confusing.
All in all, despite these issues, I found that playing music on my Android devices was simple and straightforward. Basically, you manage and play cloud-based music in the same way you do local music -- you can even include both in the same playlist. One nice touch is that you can choose to display only music that is offline (that is, stored on your local device), or your entire collection, including cloud-based music as well as local music.
There's also a nice addition to the Music player called Instant Mix. It's a Pandora-like feature that examines the song you're currently playing, then looks through your music collection and creates a playlist composed of music similar to the music you're playing. I've tried it and it worked as advertised. You can also rate your songs with thumbs up or thumbs down, and then use those ratings to later help decide what music to play.
At this point in the beta, you can't buy music and include it directly in your collection. Tap a song and choose "Shop for artist" from the menu, and you get sent to a Web page that lets you buy the music from multiple sources. However, the music won't download directly into Google Music. In other words, you have to download a song to your device and then upload it to the cloud to be able to listen to it via Google Music.
If you want to listen to your music on a Windows PC or Mac (or a smartphone that supports Flash), you can head to the Web-based music player at music.google.com . The interface is clear and straightforward. As with the Android app, you can view your collection by albums, artists, genres, and songs; create playlists and instant mixes; and give songs thumbs-up or thumbs-down.
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