I went through the same thing when I got my 8-core about a month ago. I called AppleCare and they were very concerned at first. They wanted me to take the unit to an Apple Store, but since the nearest one is over an hour away, I started the DOA process. On the recommendation of a second level tech, I took it to a nearby Authorized Service Center to be checked out before they declared it DOA. They guy in the service center said that every Mac Pro he has set up has the smell at first, so it appears to be normal in his experience. He thinks it is caused by a protective resin coating on the RAM PCB's and/or RAM riser card PCB's and should diminish over time as it burns away. It's been about 3 1/2 weeks now and the smell has almost totally gone, though I still get a whiff every now and then.
A relative just got a MacBook and I set it up for her. During the first few hours of use I noticed a smell and I got lightheaded. I opened some windows and let the machine run for a few more hours and it seems to have dissipated. Try putting the machine through a "burn-in" period to burn off any original residues.
Since my previous post from the end of June, the smell has diminished a little bit... but not too much (still enough to give me a dry throat after 2 hours).Our local Apple Authorized Repair Center could not give me any timeframe when they could check the system ("because we have so much to do") and since I need my Mac nearly every day, I am not sure when I can take it to repair(Photo by rudolf_schuba)