Rick Harper has a full batten jib for his boat (Glaser sails?). You'd have to ask him though as far as performance/etc...
On the Nacra 20, I think the full-battened jib is better in heavier winds, and the partially battened jib is better in lighter winds. The full battened jib seems to be very flat up top. This is a Nacra 20 though, not and F18, so I'll be quiet now.