I like upvotes for article comments; pretty much any place I read articles I like to be able to read them in order of popularity. I definitely don't think downvoted comments should be hidden any more now we don't have an issue with spam bots on articles. I think maybe downvotes should either be removed or at most take a comment down to 0, but not into negatives, as I think that definitely discourages people from posting opinions that they know will be unpopular even though they're perfectly valid. I'm often upvoting comments that are in the negatives, even when I don't agree with them, just to counter the fact they're in the negatives.
On the forums, the thumbs up is a nice feature in a way but, yeah, unfortunately I think it discourages 'I agree' type posts, as people just give a thumbs up instead.
