This feature is something that I think can be useful in rooting out angry pre-teens who are looking for nothing but porn. But no matter how constructive a negative review might be, many people can take it the wrong way. I think we have to be careful of this.
Maybe a test run is in order before anything is set in stone. Do a random check to see if poorly-rated reviewers are offering constructive advice, or are downright mean.
On a side note, I was reading through reviews of Johnny Rocketfingers and noticed one by Andrew Dickman, (formerly) one of my favorite artists and February's King of the Portal.. (Rockman Neo, Wily Shorts series, etc.) and his review was outright slander. If I'm not mistaken, he gave a 0 and did not offer any advice, only a piece of his mind. I went on to read all reviews left by Andrew, and found that most, if not all, were just mean, nasty things to say.. no advice from a naturally talented artist, just insults.
I guess I was surprised that one of the most popular flash artists on NG was blatently bashing another talented and popular artist. I absolutely love Andrew Dickman's work, but he lost a lot of respect from me.