I've had a brief encounter with SPD's but my knees disagreed with them and gave up after about 3 weeks. I've heard that Time Atacs give the most float and are extremely knee friendly. However, I was recently in a bike shop and the assistant advised me that Time Atacs aren't very knee friendly and suggested Crank Brothers... something like the Smarty. Now I'm really confused and wondered which is the most knee friendly, most float, clipless pedal out there? Thanks.