I see it as a laboratory to try out MSG options that you might want to experiment with and then possibly bring the result into SA.
It gives you a bigger preview window showing what any given MSG patch will do to your source image, as well as a whole array of previews showing possible MSG-based evolutions of your image. It seems faster to try things out than playing with the little MSG sliders inside SA.
As far as examples go, I thought I saw a very cool abstract one that John Dalton posted in the Forum here which I vaguely recall the caption saying was created using MSGs.
MSG Evolver is the application you can use to make your own MSG presets, or to extensively edit or modify existing ones. You can do detailed editing in the processor chain editor or you can create new msg presets via directed evolution using the 16 cell evolution grid.
But you can also use it to make abstract art or animation or image or video processing effects. There's also a rather elaborate art mapping section that lets you build a wide variety of photo mosaic image or video processing effects based off of an image or video database. The beginning of the MSG Evolver user guide in the studio artist documentation folder details all the different things you can do with MSG Evolver.
The old studio artist blog at www.synthetik.com/blog/ has a number of articles that discuss different things you can do in MSG Evolver. I'll try to get some movie examples up on the forum here over time that show off some of the things you can do.