The post from BarracksSi showing the variety of shoes available is an important consideration when you talk about clipless. Different pedal/shoe combinations can give vastly different experiences both on and off the bike.

I've seen countless posts complaining that clipless shoes make a lot of noise and are difficult to walk in for any distance. That's true in a lot of cases but not all. With the PI X-Alp series of shoes and egg beater style cleats for example, you can walk all day with virtually no clicking. They're very flexible and comfortable off the bike as well as on. You do however lose some of the advantages of clipless shoes and pedals by having such a flexible sole.

Likewise, modern Shimano and Look road cleats aren't nearly as bad for walking as they used to be. Lake even makes a road shoe with a fair amount of rubber on the bottom which is much nicer to walk on than a typical road shoe, though still stiffer than a regular shoe.