Even as something like Yahoo search has approached parity with Google on core results -- in fact sometimes surpasses, when I'm trying to find a document I know exists somewhere -- Yahoo has neglected to do some little, easy things that could help make it my primary search.

For example, no "define:" operator, and their calculator/units-conversion isn't as good as Google's.

I know these aren't key to the mass-market, but really: why let tiny things -- things an intern could add -- remain as gaps compared to Google? It gives me the impression no one is minding the store, methodically fixing everything that could prevent a person from switching.