I'm going to make a trip to The Running Company http://www.therunningcompany.net/ and make a point of meeting with a staff person to get one-on-one advice as to the best running/fast walking sneakers for someone like me: Bad knees and no arches. They do that kind of consultation. Before I go, are there any shoes you can recommend and attest to? Anything I should look out for structurally/materials-wise? Or is this more a case where I just have to be careful no matter what shoes I get?