A good design (like a good scientific theory), like the Chinese wheelbarrow, not only makes the job it's designed for easier but also opens the way for new uses not possible before: I was struck by the wheelbarrow train concept that this design enables.

I also find it interesting to think about the interplay of effects on innovation, e.g:

"It is thought that the primary obstacle to large-scale development of the wheel in the Western hemisphere was the absence of domesticated large animals which could be used to pull wheeled carriages." (http://en.wikipedia.org/wiki/Wheel#History)

Note that the wheelbarrow is primarily for human use, but it's not possible without the wheel which, (it is conjectured) is invented to carry loads with the help of domesticated beasts of burden. So, the American peoples could not go through level I (invent the wheel) due to the shortage of domesticated large animals, to arrive at level II (invent the wheelbarrow) which would have freed them from relying on such animals.