I installed a box similar to the one B&D recommends, based on his recommendation. It comes with two spare breakers installed, and spaces for additional ones. Right now those breakers are unused, and serve only to confuse anyone who tries to run the generator when I'm not home. But they would be very handy if I didn't already have an outside receptacle close to the disconnect. The spare circuits are on the house side of the box, so they are live whether you're on the grid or generator.
I looked at the lockout devices, but thought they were overpriced for a piece of sheet metal and a couple of screws. Plus I didn't want to sacrifice two slots in the breaker panel for the generator.
The Reliance transfer switches sold by the big box stores allow you to power a limited number of circuits, but not the whole house. This is a non-starter for me. I like the simplicity of the main disconnect transfer switch. It's very easy to install if you already have a separate main disconnect and the difference in cost with the other style doesn't amount to much. Now if you don't have separate main disconnect and main lug panels, installing a main disconnect transfer switch could be quite difficult.