I mostly use chopsticks when I eat sushi, because I dislike getting my fingers dirty when eating.
I also like to flip my nigiri upside down, dip in soy and then eat it in one bite. I get a better taste for the fish then, which is what I am paying for, right? If I really wanted to taste wasabi syrup paste, I could buy it at the asian market for $0.99 and make a big batch of it. But why hide the flavour of the fish I am paying $2 - $5 a piece for?
Or, $5 - $15 if I am in Japan - damn, sushi is expensive over there!