I love this. I agree with the "about" that it's visually compelling, and I'm mesmerized.

This doesn't detract from my enjoyment the site, but for trip planning I'm a little skeptical of the results around the edges, especially when I'm assuming multiple transfers would be required (e.g., Local -> Express -> Express -> Local).

With a caveat this was over 10 years ago (~2012-2013), and train frequencies may have changed:

I used to live pretty far up on the upper west side, and took the 1 train from the 103rd street station daily. My weekday route was 1 -> 2/3 -> 7 into midtown. The 20 minute radius is accurate at peak times, when it only takes 2-3 minutes to catch a transfer. However, the website "about" makes an assumption this is for noon on a weekday. I don't think I ever made it to Brooklyn in under 40 minutes.