We have been using this extension on four of our websites since 2011 and are very satisfied. We are a project management training company and we use this extension to simulate the certification exam that our students are preparing for. The features that came out of the box were not a 100% match of how the "real" exam is designed in regards to look & feel. So we had the extension developer customize it for us. The customization was done to our utmost satisfaction and the tool has been functioning without a hitch. So far our students have taken nearly 10,000 simulated exams using this extension.
Initially, we felt that the cost for customization was a bit on the pricey side. But once we had established a good working relationship with the customization team, it seemed like the could read our minds and delivered features at an incredible pace. Their customization pricing is justified. We have been 100% satisfied with the extension and their service.