I've booked and flown a few JL awards lately. A couple things I've learned to keep in mind:
- The SFO-HND flight is extremely convenient for connections. However, because of the late departure, the meal service is not as elaborate as other F flights since most people will sleep right away. The snack menu is also different from the other F flights. But the flight is incredibly convenient.
- You can only book Y for domestic JL segments. Paid upgrades at the airport are very inexpensive, though (it's between 900 and 1000 yen one way--less than $10).