SPD's are good for nipping to the shop etc as you don't need to change shoes when you get there and change back when you leave, you can easily walk in a pair of MTB shoes. I use mine all the time and if I need a spare pair of shoes just carry some in a bag. Personally I think road shoes for anything other than serious training or racing are a little over kill as they can be quite limiting.
SPD's are good for nipping to the shop etc as you don't need to change shoes when you get there and change back when you leave, you can easily walk in a pair of MTB shoes. I use mine all the time and if I need a spare pair of shoes just carry some in a bag. Personally I think road shoes for anything other than serious training or racing are a little over kill as they can be quite limiting.