I've been a serious runner for many years. Unfortunately, between running and playing hardcourt tennis since I was a child, my knees are in pretty poor shape. I've tried to start back running recently, but my right knee especially has given me a lot of trouble. So I've decided that it may be time to find a low impact exercise that still give me a good cardio workout without the strain on my knees. After talking to a friend, he suggested an eliptical trainer. I had never heard of one, so I did some research. I like what I've read, but would like to hear a few more opinions before I buy one. Anyone here own or use one regularly? And if you do, what do you think?