I think you can do better than the public review systems that exist today: you can authenticate the buyers, which improves the usefulness of the reviews. Your reviews cannot be stuffed by hyper aggressive sales members posing as fake customers.

And, a step above: you can show how ratings from the same buyer change over time as their price point, scale, and features evolved. (Solve for: would you rather buy a piece of software that makes you happy as hell on day 1 but miserable on day 366, or one that makes you modestly happy on day 1 but blissfully happy on day 366?)