STEVEN GOODHEART This program does a terrific job of putting beautiful moving images on your desktop. Most of the built-in Quartz Compositions are beautiful and interesting, and it's also really cool being able to display a live web page on your desktop if you want.
But the big thing for me is how gracefully Mach Desktop handles running QuickTime files on your desktop. I have dozens of beautiful, and really huge, QT files, and Mach Desktop plays them all with ease. The QTKitserver that runs in the background seems to take way less cpu and memory than other ways I've tried to use to run a QT movie on the desktop -- like using Screeni, or SaverDesktop, or WallSaver to run the SaveHollywood Screen saver (it plays QT movies as a screensaver) on my desktop. Alas, SaveHollywood broke with Snow Leopard, so I can't even do that trick anymore.
After using Mach Desktop all morning, and trying out all kinds and sizes of movies, the Quartz Compostions, and putting different weg pages on my desktop, I was sold. The interface is easy to use and the prefs are a breeze to set up. It just works. I think it's a great buy for just $10, given all that it does, and best of all, it doesn't overtax my machine that way desktop screen savers, for example, seem to do. Highly recommended. The only problem I have now is that my desktop is often so engaging and beautiful, I just want sit and watch it!