Increases base attack power by 2.
User cannot be targeted physically.
I could be wrong, but Reflected spell attacks can target the user while in Jump status, although this will fail miserably. This implies there may be issues in targeting while under Reflect (like all those hidden spells that were dummied out in FF2 US. This is more notable behavior with Evilmasks. Not sure if this is fixed in FF4A.
FF4A Specific: Double Jump seems to consider the attack a result of 2 Jumps.
New Edit: Time to command execution is based on Agility. Consider the effect of the Blood Spear early game.