I didn't realize this - thanks for sharing. 
How does Charisma factor in to passing a Speech check with NPC's?

How does Charisma factor in to passing a Speech check with NPC's?
Charisma directly affects your starting skill in Speech. But I'm almost certain it doesn't affect the Speech check itself. From the Fallout 3 wiki (Value=http://forums.bethsoft.com/index.php?/topic/1121426-speech-tag-skill/Charisma):
Value Skill Modifiers
1 Barter +2, Speech +2
2 Barter +4, Speech +4
3 Barter +6, Speech +6
4 Barter +8, Speech +8
5 Barter +10, Speech +10
6 Barter +12, Speech +12
7 Barter +14, Speech +14
8 Barter +16, Speech +16
9 Barter +18, Speech +18
10 Barter +20, Speech +20
Charisma *might* help to give you a higher starting disposition with people. It *might* even open up some dialogue options, like Intelligence can. But I'm guessing. I don't remember the early Fallouts or Planescape:Torment having Charisma option in dialogue, the Fallouts stuck to Speech.
Sigh - now I want to take Speech as a tag skill. Back to the drawing board . . .