Interesting, do you mean contrast between non-roads and roads, or between map and text? I think (bear in mind I have some color blindness) that it's gone from a low-contrast road grid with high contrast text to a high-contrast road grid with low-contrast text.
It would be easier to trace the shape of the roads, but that's not how I personally use a map. I'm much more focused on the name of a neighborhood or the name of a road, and its relative position.