I needed a component that would allow me to have very structured content with granular ratings, and this absolutely did the trick! I am not using it for product reviews, but rather to allow users to discuss, comment on, and rate a large and complex topic represented by a single item. Before jReviews, I was going to have to create one category per topic, then individual content items to represent the complexity, then a menu. Argh. Or, create a form, but then I wouldn't have had the rating.
So the point is, jReviews can be used -- with some deep but manageable customization -- as an advanced content management+commenting system.
Only complaint: this relies on patTemplates which is in theory good, but it is a bit hard to manage, slowing down template customization.
Finally: the support has been AWESOME. Responses are almost immediate.
This is one of those few components that is sooo worth the money.