I think the video shows the heaviest grass/weeds it can handle. As long as you are using it within it's capabilities, it seems like a nice machine. For mowing side hills without risking injuries from falls, it might be worth the money
For me personally, I would need a machine that could handle much heavier brush. Typical brush around here would contain much more fibrous plants and small trees.
Seems like a well built niche product.
Safety is certainly its forte especially on angle slopes, or perhaps in electrical yards and other areas where a person might be at risk.
Cost and range might be its detractors.
I wonder if they will also offer GPS control?