It states in the manual that Charisma is important to Bards. How is it important (except min. class requirements and reaction adjustments)?
Speaking of Reaction Adjustments; is it only the Character speaking whose Charisma is relevant, or is it a party thing? And, if it's a party thing, is the Charisma of the party totaled or averaged?

AFAIK charisma is impt only for the leading character (the one in the #1 slot) and it affects reaction of NPCs.
It's not as impt as say in Planescape:Torment where a high charisma could allow you to solve quests in a non-violent way.
But there is a limited number of dialogies where you could get some additional xp for saying the right things. Not sure whether charisma plays a role in the dialogue choices that come up, though.

Thanks Hayashi.
I wonder if you have any advice on my other post? (Images?)
Thanks again,
-Bjorn

Charisma is important to the person that you have doing all of the talking. You let that character speak for you in the stores, and try to get a price reduction in the process. As for reputation, that is worked out on a team basis, though I've never really seen it's effects in IWD (unlike BG). Your actions, or lack thereof, improve or remove reputation accordingly.

High Charisma is useful in several quests where you can get some added XP. It's especially useful in the following quests:

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1) You convince Jed in Easthaven in the Prologue that his drinking isn't productive and get extra XP that way

2) You champion the faith of Ilmater to the villagers in Kuldahar (extra XP for Paladins or Priests with high CHR)

3) You attempt to negotiate with Mytos in Kresselack's tomb to a peaceful solution (doesn't work, but you get mondo XP for attempting it)

4) You convince one of the brothers (Flozen) in Marketh's Hold in Lower Dorn's Deep that he's a born artist, and get him to leave to become an artist (peaceful solution rather than fighting him)...a LOT of XP for this one, much more than merely fighting him.

These are just a few of the additional "quest" options you can get with a high charisma. I'm sure there's others I've forgotten about.

Cheers,
-Sazerac