I've had one for about 3 years now. I use at least 2x a week, usually more to supplement my workouts. I love it, but I do know some who don't care for it. It does only go up to 4 mph, but you can adjust the tension/intensity from 1-12. I wear a HRM on it, and when I'm using it as a climber, I can get to my upper zone at about 3.3 mph. You can lock the treadles and use it as a treadmill with an incline of 10 (I think--it's pretty steep), and then I usually go to about 3.5-3.6 mph. I would advise you trying to find one to try out first. It is true about tripping if you don't keep your feet straight on the treadles, but I've mastered that and usually don't hang on either.