I’m not sure exactly what the draw is to USB displays, but I guess for some people it’s pretty handy. If you can get daisy-chaining to work, it could be nice, but there are data bandwidth issues when you’ve got a lot of information going over that cable. In any case, they’ve released a beta driver set for Intel Macs and “even” MacBook Airs.
Thing is, it doesn’t support any kind of acceleration, so any kind of hardware-based tracking, smoothing, filters, or hardware handling of codecs is inapplicable. Bad news, but chances are if you’re using USB as your primary display connection, you’re not using too much hardware acceleration. It looks like there are a lot of limitations, but it is beta after all.