I absolutely like the idea that as a player you won't be able to actually see the character's affinity level represented by numbers. That's what I dislike about RPG's, and why they just don't cut it with me: they're usually presenting some sort of world that's supposed to be a place you can really get sucked into, but at the same time everything is about numbers and 'upgrading' and reaching the next level in what is so obviously a game. And those two things, for me, simply don't work together very well.
'Outcast' did use an affinity system kind of like yours, although I'm not sure how many levels they used: could be three, maybe five... 'Levels' in this context being the possible different ways of how npc's would respond or react to you, not the actual number of 'points'. They used this both with random npc's and with important npc's. I think you could even be in the middle of helping an npc, and when their affinity dropped severely (because they saw you murder several innocent people, for instance), they wouldn't even be bothered by your attempts to 'finish your quest', they'd just tell you to get lost, you piece of Zort! Admittedly, I could be partly wrong about that because it's been a while since I last played it, but hey, it sounds good
