As a regular bike rider in Manhattan, it would make things a whole lot safer for bicyclists, and for pedestrians, who often blindly walk in or cross bike lanes, usually while texting. However, as you say, they would look awful and be very expensive, given that we have so many bike lanes throughout the city.
There is someone here who worked on designing that pathway or something similar in nyc. I just glanced at post so dont remember what he said. Maybe he will appear