The "User Ratings" section represents the average score for a video card in 6 different categories. These ratings, as the name suggests, come from our users. There is no scientific process for determining what card gets what rating. If you see a better card with lower ratings than a worse card, it is because of this process of site visitors voting freely on the cards.
To keep things fair, I ignore all ratings which are more than 40% off the average score. For example, if a card has an overall score of 9, and you vote 0, your vote will not be counted. This is simply to stop certain types of people from trying to vote down scores of cards they don't like for whatever reason.
You can only vote once for each category for each card.