Here's a clever idea. I'll admit that I'm superficial enough to think more of a given application if its installer is on a well-designed disk image. AppZapper and Delicious Library immediately come to mind. While I simply admire them from afar, blogger Roustem Karimov is on a mission to find the best one. He has posted snapshots of several images to his blog, and he rates each in terms of appearance, how clearly information is presented and so on. Check it out, it's rather interesting.
[Via The Apple Blog]