I have the M520's on both bikes. I really like the idea of being able to clip in on either side and not have to worry if the pedal is in the right position to clip in. If I need to ride with regular shoes, I use my Decksters that just snap in on one side and give you a better platform then the A530's.
Platforms for any clipless pedals are easy to make and you can use any type of material, including plywood. All you need is an extra set of cleats.