I’ve ridden the portion between N. Canaan, CT, and Philadelphia twice in the last several years, including in 2018. I’ve got a few quibbles with it, including the use of the Walkill Trail south from New Paltz, NY (not suited for skinny tires), but overall, think it’s pretty good. They really nailed the portion in NJ. The Harlem Valley Trail south from Millerton, NY, is also quite nice. From there you can save some miles if you don’t mind some fairly benign dirt/gravel.