I have been here many times, with family and friends and I'm always happy with my stay.
We mainly come for the indoor waterparks, but they offer more than that. In the winter months they offer horse carriage rides and snow tubing. The carriage rides are free, but the snow tubing costs a few dollars per person. We had a blast.
There are also several ski/snow boarding places nearby too. We have done that on previous trips, too.
They only negatives would be that it is quite pricey to stay, but if you get a few friends to come to split the price it is quite reasonable then. And the waterpark areas are usually pretty crowded, but much better then an outdoor waterpark in the summer!
It is very family orientated, but a young or old couple wouldn't feel out of place.