Ok everybody, here it goes again.
I know that there have probably been multiple posts about this, but I have yet to get a clear answer on the Fiendish sorcery class feature on Tieflings. the entry states: 
Fiendish Sorcery: Tiefling sorcerers with the Abyssal or Infernal bloodlines treat their Charisma score as 2 points higher for all sorcerer class abilities.
The purpose of this is clearly to offset the natural -2 to Cha that tieflings suffer due to their inherent alien nature, which would prevent them from forcing their self/ideas/personality on others around them in the world, and how much they pay attention/listen (not how good they look). The more Cha one has, the more people pay attention and listen to their ideas. However, this does not tell me which abilities it modifies. 
Obviously it would increase the times/rounds I can use the 1st level bloodline powers of each bloodline. I would assume it would increase the spell DC of my spells. But does it give me bonus spells? and what about skills? I mean I get that tieflings would have a natural disadvantage in the diplomacy department, but Use Magic Device? Bluff? Disguise? INTIMIDATE? all of these the tiefling is supposed to be (stereotypically) good at.
Any clarification would be helpful.
Also, on a side note, I would say that if you are playing around with alternate Tiefling heritages (e.g. Daemon- or Rakshasa-born) then they should be able to use this feature when taking those respective bloodlines.