from what I understand in the docs it's more kind of a customizer for windows default behavior by defining "rules", like always open the mailer in the upper-right corner. Isn't it?

I need more little individualized solutions for different projects like adjusting emacs, firefox + error-console and/or different other browsers. So calling several little scripts is more what I need.

But I think devilspie is in general a good and necessary extension to metacity! 8)