I've only flown the JFK-YVR portion, so can only report on that part. Cathay's HKG-YVR-JFK routing is a great deal for those of us in Vancouver, as they offer great prices to NYC from Vancouver, compared to UA,AC,AA,CP et al. plus the flight is non-stop on a 744.
Also the service, entertainment, comfort are all miles ahead of the North American standard. When I took this flight recently, I thought the cabin service was a good as I've ever experienced anywhere in economy, esp. on the JFK-YVR portion.
You're are in for a great (albeit VERY long) flight on CX. Enjoy.