Very quiet and smooth
My roommate can't even tell I'm working out. This really is a great product. I can shift through all 27 gears with no problems, although I primarily only use 3-5 of them. Indoor training is pretty tough since there are no physical landscapes or weather to battle, forcing you to change your amount of effort. So I videotaped a few drives on some mountainous scenic routes and watch the DVD on my HDTV when I'm on the trainer. When the video is going uphill, I put out more effort. And less effort when the video is going downhill. It's the best I can do to make my own interval training, and still enjoy the workout.