Man, mine is completely different, but comes out the same as what I'm reading from everyone else.
I got my recipe from Tanith Tyrr, The Bay Gourmet:[url='http://members.tripod.com/~BayGourmet/primerib.html']The Perfect Prime Rib[/url]. The gist of it is 250* oven for as long as it takes, and a meat thermometer to check for doneness. My only issue is what constitutes rare, or even medium rare; for me, pulling the roast at 120* is impossibly rare, regardless of what people say. 130* is more like it, leaving ends well, center medium-rare, and the inbetween pieces medium. When I pulled it at 120*, I spent the next 15 minutes browning slices under the broiler for people.
( This might be because at the 250*, my roast doesn't get that temperature climb that others have described; I've never gotten as much as 5* change, using a digital thermometer.)
I've been serving a 4 rib roast every Christmas for about 10 years, and I have one tip on serving: People seem to prefer thinner slices instead of "restaurant cuts". Maybe it's because a holiday meal has so many different aspects, and the meat, while delicious, is not as much of a centerpiece, what with many other dishes on the table.