Ussop's hardly the normal man with Yassop as his father. He is an outcast of society just as every member of the Strawhats are.
Ussop is not truly a coward, but everytime he fights, he fights with fear overwhelming his warrior instincts. Fear is his Achille's Heel, but otherwise, he'd be an awesome combatant. He can usurp tactical advantages with tools and battlefield, and shoot with needlepoint precision.
Nami basically fights a similar way but with elemental magic powers.
i think ussop will develop to become a strong sniper durin the seriez n will gain mo strength n mo knowledge durin the course of each battle. Who knowz he mite go up against hiz dad 1 day in a deul.