I use Shimano 545, which are similar to the 647. The "platform" isn't really one. It's a cage around the SPD and I believe it's there so MTBers can still apply pressure when unclipped. They work as platform for short errands or emergency but the SPD mecanism sticks out so it's a little uncomfortable and slippery for long rides. Another benefit of the cage is the pressure is spread over a large area and prevents hotspots many people complain about SPD. I like them and unless I go platform-only, my next pedals will be of the same design.