Let me put it this way. I've had mine for almost 10 years now. I still use it year round on a regular basis and enjoy my workouts on it. It really does work the ski specific muscle groups that help you get the skis out from under you as you move them from side to side. It also works well with keeping your balance centered.
I'm really considering upgrading to one of their new models (the S5) where you can actually click into the platform while in your ski boots and the platform can also be angled forward a bit to really simulate the forward lean you encounter while heading downhill! Verses the S3 model that I have where I'm in my sneakers and the platform stays at an angle that is parallel to the floor
They are very well built, reliable machines too, with the only maintenance I've had to do on mine being replacing the rubber resistance belts twice now (about once every 4 or 5 years)
Cool. Prices for the top-end models are pretty steep if it was just a novelty that would end up collecting dust after a couple months. Good to hear it helps with ski specific muscle groups, too. I can't get out during the season as often as I would like and always end up feeling it afterwards. It would be nice to maintain those muscles in between outings.