An interesting article regarding the current glut of USDA prime beef appeared in the Wall Street Journal on 7/15/09. It features a great passage contrasting Grass-fed beef with USDA prime (heavily marbled) beef:

By contrast, grass-fed meat, which comes from cattle that haven’t been fattened on grain towards the end of their lives, rarely earns the prime grade because it tends to be less marbled. But it can have a more complex flavor, with herbal notes that reflect the grass diet, and it is also healthier than corn-fed beef, with more omega-3 fatty acids and less saturated fat. This meat benefits from a sprinkling of melted butter or olive oil. For the ultimate garnish, Mr. Raichlen [Steven Raichlen, host of public television’s Primal Grill and author of “The Barbecue Bible”] recommends making a cup of aluminum foil, filling it with a piece of beef fat, and placing it over a cooler part of the grill until it melts. Pour a little liquid fat over a cooked steak for a beefy enhancement, he recommends.

Here is a link to the complete article