I've been having issues with self linking css3 PIE in my theme so I figured I'd give this plugin a shot, but sadly the file that gets generated writes to the root of my install which is a Multisite install. I have over 90+ clients in this install so if I tried to apply this plugin to other sites, it would over write each instance each time I visit the the WP PIE admin screen.
Also, the plugin activates and writes a new file to my install, but the file is blank. Not sure if that's because of it being on a multisite or what? But there's definitely a limited scope with this plugin. I'd suggest checking into making this multisite friendly.