Multimodal, wearable technologies have the potential to enable a completely immersive teleoperation experience, which can be beneficial for a number of teleoperated robotic applications. To gain the full benefit of these technologies, understanding the user perspective of human-robot interaction (HRI) is of special relevance for highly advanced telerobotic systems in the future. In telerobotics research, however, the complex nature of multimodal interaction has not attracted much attention. We studied HRI with a wearable multimodal control system used for teleoperating a mobile robot, and recognized a need for evaluation metrics for multimodality. In the case study, questionnaires, interviews, observations and video analysis were used to evaluate usability, ergonomics, immersion, and the nature of multimodal interaction. Although the technical setup was challenging, our findings provide insights to the design and evaluation of user interaction of future immersive teleoperation systems. We propose new HRI evaluation metrics: Type of multimodal interaction and Wearability.