Trains also leave every 7-10 minutes, no goofy security checks etc.

Buy the railpass if you don't hold a Japanese passport, it'll save some $$. They can be ordered online through JTB (which is a Japanese travel agent) and other groups if you can't find them locally.

To actually tie this in with NW, you can get an intra-Japan award as well at 15k miles which is a fair deal but it's really a steal if you're going from places like Fukokua (I love their airport code, FUK ) or Oita up to Sendai or Sapporo.