I came across the "reverse sear" method about 6 or 7 years ago, when researching the best way to cook prime rib. I read an article on the technique, comparing it to the "traditional" method of searing, then cooking. The author had really good pictures and analysis, and I was hooked!
If you "brown" the meat first, and are going for a medium-rare to medium finish, you will end up with a 1/4" or more of medium-well meat at the surface (the gray ring). This is ok if your cooking pot roast, but not cool on a nice cut of prime rib!
By slow smoking (or cooking in the oven) at 200-210°, then searing after, you end up with a paper-thin crust, and pink all the way to the edge! Amazing how well this works.
I also use the reverse-sear on things like sirloin tip roasts (poor mans prime rib) and pork loins. Loins don't develop a bark, when smoked at 225° to IT 155°, so the reverse sear (on the grill, for me) gives them a nice crust, but keeps the inside moist and tender!