Personally, I don't like the idea of a voting system, for a variety of reasons, outlined below:

[list][*] It's a hackneyed trope. That doesn't necessarily mean it's bad, that just means it's overused. It's not original. It's not inventive. There's a certain outcome, so it's incredibly predictable. In short, it's boring.
[*] It's a classic trope because it's easy, and easy doesn't necessarily mean good.
[*] It plays off the idea of a mob mentality, and that only works when you have cohesive groups. We are each playing as individuals, and I've never seen a mob mentality actually form in an RP with such talented writers as you all. We're too attached to our characters' individual belief systems to let them fall into the trap of peer pressure. Therefore, it would work out in such a way that no matter who is voted off the island, the majority of the players would be dissatisfied with the results.
[*] It will get rid of players/characters twice as fast. And half of all character deaths will be predictable, and boring. One half will have exciting, heart pounding, thrilling escapades which lead to their demise; the other half will simply be voted to death, and follow through to a boring ending. It's predictable, it's boring, once again. It lessens the suspense, cheapening the story.
[*] If we didn't have a voting system, it would be on us- or rather, our characters- to take up initiative and find out who the culprit is. Having a voting system makes it so that our characters don't need to individually attempt to figure out what's happening. It makes it so that we can be lazy, and just let the murders happen, then vote someone out, then wait for another, etc. If we didn't have a voting system, there would be nothing in the way of the murderer but the drive of the characters not to want to die. It would give us a better chance to develop our characters. 
[*] A voting system will lend to the killing of innocent people, sure, but don't we already have that with the murders? Don't we already have the "psychological conflict between your characters and [mistrust sown] in the group"? And, if there was no voting system, wouldn't they have to "come to terms with being 'responsible' for the death of this person", the person in question being the latest victim, given that your character did not take the necessary steps to stop the murderer? [/list]

In short, it doesn't add anything that I can see, it takes away opportunities, suspense, initiative, development... etc.