The shiny new Boxee Beta didn't launch with Apple TV support, but there was a geeky hack to load it up. Now it's much, much easier to install, or upgrade, the Beta onto Apple's would-be HD media centre.
If you'd already loaded an Apple TV with the Boxee alpha, you should simply be able to head to your "Launcher" menu, head to Downloads and upgrade the Launcher itself, and then upgrade Boxee to get the Beta up and running. If you're installing the Beta fresh, you can follow these instructions or, if you're already hip to the how-to of this sort of thing, just grab the updated ATVUSB-Creator, unplug your Apple TV, stick in the upgraded USB drive, and then power back on.
We haven't tried out the Beta on our Apple TV rig yet. Apple's somewhat under-powered media device will never provide exactly impressive HD video performance, at least compared to other modern media centres, but some forum posters report a more efficient operation with the beta. If nothing else, it's a much nicer interface.
Get a bite of this – Boxee Beta on AppleTV [Boxee Blog]