I have one, and I love it. Although I probably only use it once a week - I like to vary my cardio. I did use it a lot when recovering from a knee injury, it is really easy on the joints.
It is a lot smaller than a treadmill and not as quiet as some of the really nice treadmills. It is a great workout, your legs have to push through every step. You can change it to treadmill mode - but it does not have incline. I searched google and found a local dealer so I could go and try it out first.
If you love doing cardio on a machine go and try a bunch of them out, side-by-side - because they are expensive.