I found the O'Connell scenario to be probably the closest (and in my mind the most realistic) scenario about what might have happened. It's extremely similar to the "Dispatches" thing I whipped up in the writers' forum not too long ago. About the only problem I had with O'Connell's story was the relative lack of devastation in Western Europe.
While the Soviet Union was extremely behind in the arms race in 1962, they did still have over 2,000 nuclear weapons. Now, most of those couldn't reach the United States (there were fewer than 24 active Soviet ICBMs at the time, and many of those may be knocked out before launch, due to the lengthy fueling time), and bombers would be flying into the teeth of one of the most intricate air defense systems ever designed. But that won't help Western Europe, which is in range of dozens of IRBMs based in eastern Europe. It won't be pretty.
The end result is a hurt United States, a wasteland Europe/Soviet Union, a superpower China, and a world largely dominated by the Southern Hemisphere.
The U.S. makes out fairly well in such scenarios -- ironically, Canada will fare fare worse, as Soviet bombers damaged in penetration attempts had orders to hit the nearest viable target -- but you can count half a dozen to a dozen American cities outside southern Florida as destroyed. Southern Florida itself may be written off entirely, depending on how you have the war in Cuba play out. Key West is definitely gone -- it's in range of FROG missiles -- and Miami is a viable target as well. North of the line Tampa/Cape Canaveral, things should be all right, however.
It's a scenario I've studied for a long, long, long time, given that I live in Key West, the virtual epicenter of the Crisis. Chris, I'd love to work with you on this. There's a boatload of primary sources down here, and I can look up pretty much anything as needed.