It really comes down to the right tool for the job. Just as I ride different bikes depending on the type of ride, I also use different pedal types.

I answered above Look pedals and Sidi road shoes. This is what I use on my favorite bike which is the bike I use for long, fast rides. There are other setups that would work well enough, but not quite as well as a true road pedal with a true road shoe. For the small amount of walking I do during a ride on that bike, the minor difficulty of walking on the cleats is not important, especially using Kool Kovers over the cleats.

For commuting or riding under 20 miles to a place I will spend more than a few minutes walking around, I go with either Crank Bros. Smarty pedals and fairly flexible MTB type shoes, or clips and straps with regular shoes. The choice comes down to whether it means more to me on that ride to wear regular shoes or to ride efficiently. Often I'll just go with whatever happens to be on the bike already.

For times that I'll be on and off the bike a lot, like riding around town shopping or visiting, I'll go with regular shoes and platform pedals, with or without clips and straps.

On my MTB, there's no decision. I always ride with Eggbeaters and stiff soled MTB shoes.