As you all probably know, on 2/15/07 the preview of DreamScene was made available to those who have the Ultimate Edition of Vista. I myself am one of those people and so I was able to download it through Windows Update. All I have to say is that it is pretty dang sweet. I won't be putting any videos as my background yet since there are no good ones available yet, but I am using the default Windows DreamScene Content, which is basically a moving representation of the basic Vista background you see when you first install Vista. It doesn't have any very subtle changes, but rather just enough to let you know it's there and is very cool to see.
I know a lot of people say it takes up too much CPU, but the cool thing is, when your desktop isn't showing, then the animation isn't running and your CPU speed is near nothing. When I have my desktop showing, DreamScene takes up about 10% CPU, with spikes up to about 13-15%. When I have a window maximized, my CPU level drops to 0-2%, which is normal.
Just wanted to let you all know that it works very well and I can't wait until the final version is released so that I can see what the waterfall and rain look like which were shown during a DreamScene demo by Microsoft.