In software development it is hard to know both whether the team has developed a product that fits the users’ needs, and is easy to use. One way of gathering feedback from users on both these issues is to conduct formal user testing, which has been rated by IT professionals as one of the best methods for user involvement in software development. In this paper, we present a formal evaluation of a running prototype for a virtual reality experience that was scheduled to be launched 3 months later. We conducted formal user testing with five users, and recorded the problems that the users experienced while they used the VR prototype. We also collected data concerning each user’s impressions of their experience immediately after it was complete. The results show that many serious problems were identified, and that the developers found several of them to be very useful. In some cases, the user testing was regarded as having been essential to discovering these problems.