My upvotes/downvotes are worth 2 points each and my supervotes are worth 6. A person with between 10 and 100 karma on the forum has an upvote worth 1 and a supervote worth 2 (the scaling system is described in this code here I think)
My concern is that this system lends itself to groupthink, whereby the dominant views or topics are liable to get more karma, giving holders of those views more voting power, giving users that makes posts they agree with or that they see as relevant more karma, etc.
Dissenting opinions or posts not of interest to the in-group are liable to be downvoted (although karma is meant to reflect quality or relevance of a post or comment, this is of course misused), which both hides those comments but also puts off dissenting voices from commenting/posting in the future.
The justification for the current system is that people with more karma are more likely to be have better understanding and judgement, less likely to be sockpuppets or trolls and so are better positioned to vote. This is a system ported over from LessWrong (described here).
Concerns about the scaling system have been discussed on the forum previously, for example here.
Is this system more beneficial than harmful?
I think that the upside of the system is high, and that EA Forum posts have been pretty effective in changing community direction in the past, so the downside risk seems low. My impression (as someone who has posted things that aren't particularly popular at times) is that well reasoned-but-disagreed-with posts still get lots of upvotes.
This presupposes that the way something gets to change community direction is by having high karma, while I think it's actually about being well reasoned and persuasive AND being viewed. Being high karma helps it be viewed, but this is neutral to actively negative if the post is low quality/flawed - that just entrenches people in their positions more/makes them think less of the forum. So in order for this change to help, there must be valuable posts that are low karma that would be high karma if voting was more democratic - I personally think that the current system is better at selecting for quality and this outweighs any penalty to dissenting opinions, which I would guess is fairly minor in practice