Here's what I think so far:
Aggressive: OK in some ships, but they need to be expertly outfitted. You also want Damage Control 10 on every Aggressive officer if possible. Make sure you control which range they will engage at by taking note of the lowest-range weapon you give them. Good Aggressive ships: SO Lasher, SO Enforcer
Steady: Nuff said
Cautious: Kept my Buffalo II alive for like 15 battles. Also used in a beam wolf and in needler-equipped support ships to great success. Seems like a natural fit for ships that you either want to use as pointmen or for ships that instantly die if they close in on the enemy.
Timid: Not much experience with this one. I assume it will be annoying on a lot of ships, and decent on ships like Buffalo IIs, carriers and perhaps glass cannon, artillery-equipped cruisers, destroyers and capitals.