I've noticed this as well. The closer my searches are to what (I imagine) a typical Google employee does every day (Linux/Python/Java/HTML/HTTP/CSS, English language, American locale, someone in their 20's/30's, etc.), the better it does. Google search can be incredibly good at taking a partial Linux error message, and leading directly to a solution.

The further my search is from this, the worse the results I get. I'd say this is a common theme throughout Google's software. Google Wave, for example, seemed to be aimed squarely at the "I'm a Google engineer" use case. (I assume not many Googlers ride the bus, because that's a weak point of their maps!) The Chrome commercials they're running right now are a great example: they look like something straight out of the old demoscene, that Google engineers might do in their spare time, not something that I could imagine a use for.