I don't personally care much about the red/green bar things.
As has been said above, comments are much more useful, even more so for negative rep. If I'm being unclear or I've made a mistake, it would be much more helpful if people let me know in a constructive way rather than just giving me a thumbs down. Constructive criticism can help people to write more useful posts in future. You also get the idiots who neg just because a few others did, which penalises the poster for just making a mistake (rather than being rude or a troll or whatever).
Positive rep is definitely still a good idea, it stops the forum being cluttered up with people just saying 'thanks'.