it effects you Will Saves, some of your Force Powers (better chance to succed) and comanding you followers...With a high enuff Chr they actualy do what you tell them to do (in combat) if you dont have a high Chr then they will attack whom ever they want. I found that by the time I got around to telling them who to attack they where usualy dead
Even with a rock bottom Charisma, I have never noticed my party members do anything in battle other than what I direct to them while the game is paused.
To the Righteous belong the fruits of violent victory. The rest of us will have to settle for warm friends, warm lovers, and a wink from a quietly supportive universe.
About obediance in combat, i think it's all about the script you give them. If you want them to do exactly as they are told then don't put them in grenadier or jedi/droid support, but that way they actually won't do much anything if you don't tell them to since the combat AI will be at it's lowest.
Or you can just control them yourself... that's what I've been doing since the beginning. Otherwise you can end up with wasted Force powers, grenades in your face.... it just gets ugly.
"No bastard ever won a war by dying for his country. He won it by making the other poor dumb bastard die for his country."
-General George S. Patton