better late then never right? So i found a solution to getting emerald working in Hardy Heron. i have an ATI graphics card and a fresh install with compiz installed and xorg restricted driver installed.
1.) Install "Compiz Fusion Icon" via synaptic or Add/remove applications
2.) uninstall emerald completely via synaptic <you may not have to do this. for some reason i had to>
3.) restart you machine
4.) install emerald and install themes you want
5.) go to "applications/system tools/compiz fusion icon" and start it
6.) The Compiz icon will appear in your dock/panel right click it and select "select window decorator" you should be given the choice to select emerald or gtk. Pick emerald (I know "duh" right? ;-))
it should auto-magically work now even when you restart your machine unlike the --replace hack. plus it won't crash your games when you go to full screen like the --restart hack did for me. if it doesn't, uninstall emerald (using completely remove options and make sure to get the lib emerald engine app to) open your home directory and press ctrl H to show hidden directories and make sure to delete the .emerald hidden config file as well. for some reason i had to do this, don't ask me why, i just did. then follow the steps above and you should be good.