I think that karma is a useful feedback but only at a very approximate level. If a post is heavily upvoted or heavily downvoted it is likely to be higher quality. But this is extremely approximate. The posts I've had most upvoted are rarely what I would consider my highest quality remarks. For example, this comment was relevant but I don't see any reason why it is at +24 other than some sort of bandwagon effect.
From this 2001 article:
I, at least, found this amusing.