Greg Kroah-Hartman's OLS keynote on Linux Kernel Myths is very interesting.

And by secure, I really mean it. A lot of times a security problem will be found in one driver, or in one core part of the kernel, and the kernel developers fix it, and then go and fix it up in all other drivers that have the same problem. Then, when the fix is released, all users of all drivers are now secure. When other operating systems don't have all of the drivers in their tree, if they fix a security problem, it's up to the individual companies to update their drivers and fix the problem too. And that rarely happens. So people who buy the device, and then use the older driver that comes in the box with the device, which is insecure.