I found beta 2 on the Maven repository. JBoss 6 CR1 and Glassfish 3.1 (latest builds - I think from b30 onwards) seem to have Beta2 included as well.
I'm not sure why it is not available on the Downloads page yet.
Thanks Francois, that was a good tip. I tested beta2 and it seems to solve a number of issues we encountered, it is a pity that it is so difficult to find...