I don't know exactly what features you are after, so I can't tell you if it's suitable. I can tell you there's a large number of gaming sites using jReviews. A simple Google search gives you a few additional examples that might be helpful.

Answering your specific question about the ratings, there is a single function that generates the output for the select lists for ratings in jreviews.common.php called selectSlider. You can customize it to show the ratings anyway you want.

I don't think so, but I don't have hard numbers. A few are, but many others are using jReviews standalone and some also with jReviewsEverywhere for rating of Community Builder profiles.