I was on this flight on 8/10/04. While I highly recommend any of the seats in F, if you are stuck in Y I recommend getting seats on the right side of the plane (DEF). As you fly up from SEA to ANC you go basically follow the arm of Alaska up the coast line, and the views out the right side of the plane are phenomenal.

Also, it is only a 3.5 hour flight, so it isn't TOO long to be stuck in Y, though I got elite upgrades on my flights and we actually had empty F seats on my redeye return to IAH.

Enjoy Alaska!