Hmm. You certainly shouldn't gain points for downvoting, but I don't know if negative points are deserved. In some cases, yes - I've seen posts downvoted that definitely didn't deserve it - but the majority of downvotes are probably legit and shouldn't be penalized.

As for showing who's voted for / against posts, this could be a good thing, but I think each person should be able to choose whether to have their name shown with their votes or not, and/or only people of a certain rank (or rank AND number of posts) should be able to view the names. Someone who's been here a while and posted a lot is less likely to take downvotes personally than someone new.