PG, what exactly is "a louder voice"? If an article will be raised up by two or more points by a person with bigger voting power will its submitter get an adequate karma raise? Is there a limit? Is there a bonus for the up-voter? Do you take into consideration current karma? Does voting power apply to down voting (I assume it does)?
I think there will be a temporary higher amount of voters on the New queue, seeking for a bigger voting power, which is a good thing because the good stories will get to the main site faster. Maybe it won't be temporary as newcommers will strive for power and the easiest/only way is voting the good stories soon.
However, consider this situation: A speculator comes around, voting up at random (thinking "someone will have to raise this one up") and then another one appers, seeing that a story already has 2,3 or 4 points, he could raise it up to just because it will earn him a better voting power... Will the system be able to deal with this (altough I'm not really sure this is a real threat)?
This would lead to uniformization of discourse, but I'm afraid any global opaque karma system will do that. If I was to do a news system, I'd make it so you could somehow select people so their ratings have more weigth in your view. So content would be rated on an affinity graph that is personalized for each user. A way to do this without complicating the UI is to just derive your affinities from your votes. Now this would be an incentive to vote on the stuff you find interesting, rather than on the stuff you think will be popular.