The fact that after a certain amount of snow depth, you have to use your back to lift and throw the snow.

I was doing some Googling on this out of curiosity and ran into this...http://www.wovel.com which I feel like I've seen before but didn't really understand the advantage. Without seeing the video of it in use, it looks just like a shovel attached to a wheel. But the wheel gives you different leverage points so that you can use your body weight to throw the snow. That wasn't obvious without seeing the video.