Not sure it is a wise move on Apple's part to use DP4 as the public beta. It isn't terrible, but as many have said, there are glitches. And for people that don't know what they are doing, the various glitches can be a pain in the butt. The other side of it is the public relations aspect. Many people will see this as them getting the polished version before everyone else, even though it is beta.
A lot of people are going to install it as their main OS. And when they find that a lot of their programs don't work, are spotty, or lose some of their work, they aren't going to be happy.
I hope Apple is ready for some backlash.