These are actually a few of the reasons I run so much, It is really good for your body! When people say it is bad on the knees they are just really lazy or old. Stretching and taking good care of your body in between runs is also a very important part of being a runner. It has so many positive benefits that do over rule the downfalls. Health, happiness, strength, being in great shape....etc
Also on these boards
this would be the best for running!