What are the benefits of high INT, WIS and CHA in dialogues? How much of it do I need to get nice options?

My rogue has INT 12, WIS 10 and CHA 12, and seems to be doing fine in conversation. Persuasion is an excellent skill to have, and points in it will make up for average to low charisma. I've seen the effects of low INT. Your character speaks like an orc on magic muffins.

Low Cha can be pretty annoying, too... Bah, when Solomon said something along the lines of "They told me you were ugly, but..." I simply wanted to strangle the little bugger.
That with Cha 8, by the way