Jacob, I heard that
Always remember, there's a distinction between Service Tech's with years of experience and retail store "Geniuses" who get two weeks training courtesy of apple. I like to think that my wealth of knowledge puts me in a position to better mod a mac, because I know my way around them blindfolded, whereas the end user doesnt take them apart all day, and probably hasnt read all of the apple internal diagnostic manuals.
As far as warranty goes, I prefer not to touch anything under warranty unless I order spare plastics for it. (like my ibook) I paint the spares and keep the originals, should it need to go to apple for an REA issue or similar. Out of warranty is a whole nother ball-game.
In regard to the eMacs, on many of them the dome plastics are molded in the opaque white color, and the front bezel plastic is clear, giving it the appearance of the early snow ibooks. When I modded an eMac for my shop, I went the easy way by sanding the outter surface of the removed plastics, priming them, painting them, and clear coating them. It comes out looking good, and its not as much of a pain as stripping the internal whiting can be.
Modding, its a personal preference. Not for everyone. But absolutely for me
One last thought, dust covers are all fine and good, but realize that the majority of the dust that gets into your computer is sucked in when the machine is running. The fans pull air in, as opposed to pushing it out. it gets amplified if you smoke lots around your computer (the marlboro effect) The most proactive thing you can do is to buy cans of compressed air, and blow the dust rhino's out. it takes about ten seconds and works like a charm. An old toothbrush can also clean fan blades and intakes as well. This will serve you better than any cover ever could. Trust me, I've cleaned stuff out of cases that was so thick, it caused the processors to burn out from lack of airflow. And of course the customer was shocked because she covered it up every night.
Okay, nuff from me, someone elses turn to babble!