If you're looking at a WaterRower, you're probably also considering the Concept2. They're both great machines, but which you choose depends on your needs. I think the WaterRower is ideal for most people, but not everyone. The WaterRower has a number of advantages vs the Concept 2 - it is quieter, the mechanism up front is lower profile, it has a comfortable seat, it is much better looking, it's easier to stand up when you're not rowing and it's just ... zen-like. There is something about the smoothness of the WaterRower that makes it a joy to use, and because it's quiet you can easily stream your favorite binge-series without cranking the volume too high.
From a fitness perspective, the WaterRower Natural works 84 percent of your muscle mass, helping tone and strengthen your muscles while burning far more calories than most other aerobic machines. The exercise is also low impact, as it removes all the body weight from the ankles, knees, and hips, but still moves the limbs and joints through a full range of motion--from completely extended to completely contracted.