well, since I have preordered it anyway which - from what I understand - gives me beta access anyway, the decision does not particularly affect me. I will face a slight delay (it is stated to not go out next week, as the final release was supposed to, but the tone hinted at soon afterwards). so, I get more or less what would have come out if they had not delayed it.
in general: it is one of the big points in the gaming industry (and others of course). personnally, I prefer this way, a delay, which brings a better product. no need for a buggy, or unbalanced releaes, it would only anger fans and harm reputation. that said, there is only so much you can delay, but I don't think the patience will be raped here.
bottom line: course I am not happy that the product is not ready yet, but if the hard facts require a delay than it was the right decision.
and of course I am happy to hear there is a public beta, I think the last one helped and it does benefit games to have a wide range of opinions impact on it rather than a range of internal beta testers.
as for content: what exactly will the beta testing involve? bug hunting and balance testing (which is the most obvious) or other issues as well?