Are you talking the network code, or playing? For the latter, by the looks of it, there's a free-for-all alpha playtest every month.
Not sure I've presently got a client that will play it sufficiently well to do it justice, but it looks like fun. If you click the banner back to the homepage on the site, there is a YouTube video of one of the previous tests, along with the date and time of the next one.
