I can confirm the latest build has been pretty stable, enough so that it should be fine for those people wanting to try it on a primary machine. There are still some issues with iCloud that need to get resolved, but I'm pretty happy with how it's been running so far.
Confirmed here too. I think as long as people understand that it is absolutely beta software, have backed up stuff they care about and are willing to put up with the inevitable glitches (sometimes severe) that will occur across the variety of hardware / software configurations that will be participating in the beta, life should be good.