Google said it could be days, but it looks like a good many of you -- and a number of our own devices -- are starting to see the Android Market update with Google Music. Odd that the version number of the Market app didn't change, but we're not going to worry about that.
Note that you'll also have a "My music" button available from the menu in the music section that will take you to the Music App -- and the Music App now features a handy button to take you back to the Market. Nicely done, Google.
If you're still not seeing Google Music in your Android Market, try clearing the app's cache and data (go to settings>applications and tap on the Android Market app), reboot and see if that doesn't fix things.
Thanks to everybody for all the heads ups!