Look into Campus pedals... they are SPD clipless on one side and a regular platform pedal on the other. You can wear any shoe on the platform side, and any SPD shoe for the otherside. Since SPD shoes come in styles that allow easy walking, you really end up with the best of all worlds.

Draw backs... well campus pedals do not spin around to present the clipless side to your SPD shoe. When taking off from a stop, I don't worry about it... my foot just gets on the pedal and I go. Then when a good opportunity presents itself, I flip the pedal to the clipless side and clip in (boy that sounds strange doesn't it).

The SPD side gives me more power and greater hill climbing and higher cadence abilities... The platform side lets me use any shoe.

BTW these "campus" pedals are available at Performace.