Greg's started a great converation on his blog about the internals of the DWM.
I want to take a second to note one comment that was made on his blog... Stephane Rodriguez asked about whether not the average "mom and pop" user would recognize the benefits of having a tear free experience.
It's certainly debatable, but I firmly believe that the answer is yes. Not because they have some kind of trained eye for detail or anything like that.
Here's the thing: when you move a window, and the display tears, or the window behind it flickers, it looks a little broken. When people see that, it takes away from the confidence they have in the system they're using.
With the DWM, those flickers and tears are pretty much gone. Our experience has beenthat when the average "mom and pop" user sits down at a Windows Vista desktop using the DWM, it will feel smoother, and more reliable. So while they won't necessarily be able to point out that the tearing and flickering is gone, they definitely feel better about things when the DWM is there.