Well, it won't be much of an issue for the social skills. Camlen's really the only PC with huge modifiers for his level (he can pretty much automatically turn a hostile attitude to indifferent (and a good chance to boost it to friendly), or Unfriendly to friendly, and he's only level 7- Then again, he's got dark forces pushing his targets toward believing him, so it makes sense to a degree). I'll probably just apply a similar system of modifiers to Diplomacy as there exists for Bluff.
The bigger issue, which threatens your knowledge rolls more-so, is that if you want to identify a creature of, say, 10 HD, and you roll a 19, you technically don't know anything about it even though you're only 1 point off. So I figure I'll let you glean incomplete details on knowledge checks, so if you get within a few points of the target DC you're not left in total darkness.
--pseudo edit--
@Phaedrus: Some good thoughts, I'll try to contribute to said thread.
As it stands, I know that DCs exist for a reason as a particular goal or target, but it still feels wrong that one point can make such a different. The problem is that some characters have particular backgrounds and experiences (which, I suppose, are meant to be already reflected in their skill modifiers) which lend them to having exposure to different pieces of information. It's why I like that in 4E anyone can make a skill check untrained, but they're just unlikely to do very well- Though, I did have one player in my weekly game, a barbarian, who got a natural 20 on a Dungeoneering check he wasn't trained in, giving him enough information to identify the Ochre Jelly they were fighting against.
It's not practical to do the same thing in 3.5, but I don't feel too bad giving circumstance bonuses now and again. Thistle, for instance, should know a boatload about fey, even though he has no ranks in Knowledge: Nature. He is one, he came from Thelanis, etc. I wouldn't give him free ranks in Knowledge: Nature, but I might allow him to make an untrained check to identify a fey creature due to his background, and he may even get a slight bonus depending on how common it is- the frequency mentioned by Phaedrus.