It has an extremely strong flavor. Its hotness is more akin to that of a hot mustard than the capsaicin in a chili pepper, producing vapors that irritate the nasal passages more than the tongue. To release irritation, just open mouth and breath quickly several times.
Wasabi is weak to heat, so it wont work when you put to hot foods.

When traveling o Japan it is very important to know that Soy sauce is not served as a dipping sauce. Instead of dipping your food into it totally, you just need to put the food on the surface and make just touch a bit. That is all you need to add a enough flavor to your food.

Believe it or not, it is one of Japanese dining etiquette not to leave a pool of left-over soy sauce in the little dish.