For my part, I have to say I'm not especially enamoured of the up and down buttons. To my mind, the idea runs the danger of becoming conducive to the creation of the sort of atmosphere sometimes found among the audience of crudely populist TV programmes whereby a sort of "group-think" or "collective response" can influence the expressed attitudes, or even, the desire to participate, of the rest.
If a poster likes, disagrees with, or dislikes a post why not say so in words?
Cheers