I've downloaded and tested the Hardy Heron Beta release and I could complete the installation process with no problems (I've installed without a live session, I went directly into the installation process). But then, before the first two hours of use it frozen. So I did a hard reset (the only known way out) and I stoped powernowd as soon as I could after logging on the gnome session. It then spent more than twelve hours on without freezes. It never frozen again. The next mourning I found a fully stable environment.
So... If you get a freeze even after disabling powernowd, you have to fill another bug.
I am really worried about the fact that this bug haven't been fixed and appeared in Alpha 3, Alpha 4, Alpha 5, Alpha 6 and Beta releases.