I think that most will use the rep power responsibly but then I am an optimist. I think its greatest potential lies in being able to "shame" certain users who aren't blatently breaking the forum rules but are posting tripe just for the sake of posting but add absolutely nothing to the conversation or the forum community. We have had a rash of that of late and at least for me it really detracts from the forum.
"The purpose of fighting is to win. There is no possible victory in defense. The sword is more important than the shield and skill is more important than either. The final weapon is the brain. All else is supplemental." - John Steinbeck