Originally Posted by Biff The Understudy
Actually charisma works as intended in both bg1 and bg2.
In bg1 it affects several quest rewards and can mean the difference between getting a magical pair of boots and a reputation point or a few gold coins while in bg 2 it only affects store prices and the dispositon of a few characters.
Viconia for example wont romance someone below a certain charisma point.
The charisma check however is only performed on whatever character does the actual talking in bg 1 and store prices in bg 2 is determined by the party leader (not 100% if it is party leader or talk initiator in bg2).
There are also a few "dead zones" where you need to raise your charisma several points for the next tier bonus.
For example a charisma of 10 will give the same prices as a charisma of 12 but 13 will give a discount.