Norm call and I answer, being of the 'not so keen' on clipless systems variety. Link to Rivendell Bikes article on clipless:-
http://www.rivbike.com/article/clothing/the_shoes_ruse
You can formulate your own opinions on the article, but I would note that there's a distinct lack of data, from manufacturers, supporting the benefit gains claimed for clipless systems.
That doesn't mean clipless are bad, or that they won't be a choice of preference for many cyclists. But I'm very wary of the 'night and day' differences, and vast improvements, some claim. I tried SPD's and wasn't happy, the only noticeable difference was on hill climbing and it wasn't very much. Certainly not enough to outweigh the inconvenience of having to wear cycling specific footwear, and click when you walk.
I still have my SPD shoes and one set of pedals up for sale, if you check in the classifieds. The pedals are flat one side SPD the other and the shoes a size 10.