Construction workers who have to climb scaffolding wear them here in Japan, and hiking last summer I passed a local wearing them who was gathering wild plants in the forest. So people use them to do some serious stuff.
Also, my sensei wears them to outdoor practices. Basically, they protect the feet while remaining light and giving the ability to feel the ground. The cloth on top should also fit snugly to support the ankle.
I haven't gotten a pair yet because my size (12American, 30cmJapan) is hard to find, although the jika-tabi site had some that big.
Here's just one of the many sites in Japan for them:http://www.uni-work.co.jp/web/
Keep scrolling down until you see the tabi and then click on the ones you want to see more of. You can see the price in yen, they are mostly about 2,800 yen, so the jika-tabi site isn't selling theirs for all that much more considering importing/shipping costs.
Keep in mind you need special socks too and that people are going to give you funny looks if you wear them around there!