ESPN.com has a good article on the debut of BMX racing as an official Olympic sport. Apparently it was a fan favorite and appeals to people from all over the world.
Winter Olympian Gretchen Bleiler was there watching and believes BMX racing will change the Summer Olympics the way snowboarding changed the Winter Games. Not sure if it will have exactly the same impact given that there are a lot of snowboarding events and only a few BMX racing ones. But I think the addition of an "action sport" into the Summer Games is a good thing.
As does this writer from the Vancouver Sun who also offers some good descriptions of what fans of the BMX events were privy to in Beijing.