There's a great post at 41Latitude (by way of Chartporn) that looks at all of the little tricks Google employs to make its maps more legible than competitors like Bing and Yahoo.
I use Google Maps exclusively. I never really considered it until now, but I think most of my allegiance comes Google's superior visual style. (I also find Google's point-to-point directions to be slightly better that others, but it's a pretty negligible difference.)
The article points to things like color choice, typographic hierarchy, and stroke width as contributors to Google's visual experience.
Check out the article for tons of examples. It's stuff we should in keep in mind for our infographics -- or any other project that comes our way.