http://www.fastcodesign.com/3020708/evidence/the-science-of-a-great-subway-map
Generally, I think the simplification works, particularly in the redesign of the Boston subway map. But the last example ( a weekend schedule) struck me as better for the geographically knowledgeable local than for any out-of-town visitor. The map it replaces is horrible, but there must be some happy medium that would keep enough geographic context.

As a visitor, I’d likely be looking at a potential destination, then figure out how to get there. Of course, who uses these maps anymore when every smartphone will just tell you which line to take? Although I found the hardest part of dealing with public transit that way (at least when last in Seattle) was figuring out which way to go when on foot in between buses.
Overall, an article worth reading. The visual tracking research and renderings depicting user perception are fascinating.