I've always kind of thought of beta like swimming with those "at your own risk" signs up all over the place. You probably won't drown if you're at all competent, but just in case you do, it's all your own fault.
Ok so on Friday's episode Molly and Tom basically discussed how well should a beta product should run. What I gathered from the argument was IE8 beta can run buggy because it is a private beta and Firefox can't because it is a public beta. Well never mind the fact anyone can download IE8 Beta and run it, and yes is it slow and buggy, but from prior experience with anything beta is that it is always buggy. Testing a number of these beta products I have found that this to be true all the time, public or private. The bottom line expectation should be it is a beta not the end product, thus the bugginess.
P.S. Apple pimping the SDK on their main page is so overboard. Please Steve 2 months of the Air on the front page, followed by the new the MacBook for 2 weeks. I can see this SDK roadmap photo lasting until June.