This paper investigates the effect of environmental factors on user performance in a dual-user haptic guidance system. The system under study allows for interaction between both users, the trainee and the trainer, to collaboratively perform a common task in a shared virtual environment. User studies are carried out to experimentally evaluate the users' performance while following square and circular trajectories with two viewpoints of the environment (top view and front view), while the virtual manipulator tool moves in free motion or against forbidden-region virtual fixtures. The performance is measured and statistically evaluated against task completion time, tracking accuracy, and user energy exchange. The studies revealed that changing the environment geometry from a square to a circle results in reduced task completion time and tracking error. Changing the environment viewpoint from top to front decreases the task completion time in both geometries. Forbidden-region virtual fixtures increase energy exchange by both users and decrease task completion time while compromising the tracking performance in the square-following task. However, when visual feedback is removed in the presence of the fixtures, the square tracking performance improves. The results also indicate a strong relationship between user dominance and tracking error only when the experiment is time-limited.