I just tried it again (want to be sure I wasn't imagining things), and it works.
Notably, the little Airplay icon in the lower right corner of iTunes does not light up at first. When I click on it though, the receiver is an option and then it turns on.
What it can't do, unfortunately, is turn the receiver off when you disconnect Airplay.
Also I am using a slightly older version of iTunes (10.2.2.12) for compatibility with my network server's iTunes server. Doubt that has anything to do with it though.
One final thing: If you get it working, make sure you turn the iTunes volume (i.e., the slider at the top) down under 50% before you switch to the receiver mid-song. If it's all the way up, you'll be playing the receiver at its max volume and that won't be pleasant (for you or the receiver).