I don't know about you, but to me happens a lot: if I'm reading a question with a LOT of answers, (specially in a really specific question) I just read the most voted up: that's the way the system was made to be, and it's really good. The most relevant voted by the community are the first ones.
Since we have TOO many users, and a lot of them are reading the same questions and answering them almost at the same time, do you think the "urge" to be the first to answer a question and so gain reputation points makes people sometimes write things too fast and not try to really elaborate a really helpful answer? We may think: "people aren't going to read all answers, so I need to be really concerned about how fast I'm to answer". Are we incentivating "objective answers", or "not so good but objective and good to be voted up"?
I'm not trying to be unfair with all answers people here provide, we have really good ones here. But supose what I wrote above is a reality: what you think it would happen if it was a "time delay" between an "up-vote or down-vote" and it's sum in the answer? Summarizing: what if the sum wasn't almost "real time"?