My eye gets drawn to the tradeoffs made in drawing them. For instance, often things on the surface are inked behind things below (like the monument in Columbus circle) because the things below are "more important" but this does make decoding the scene harder.

Also the S line platform in the 24nd-TimeSq station is drawn in such a way that it is not so clear what it is, which bugs me because I see that platform as one of the distinctive things about that station.