Assistive robotics have been developed for several domains, including autism, eldercare, intelligent wheelchairs, assistive robotic arms, external limb prostheses, and stroke rehabilitation. Work in assistive robotics can be divided into two larger research areas: technology development, where new devices, software, and interfaces are created; and clinical application, where assistive technology is applied to a given end-user population. Moving from technology development towards clinical applications is a significant challenge. Developing performance metrics for assistive robots can unveil a larger set of challenges. For example, what well established performance measures should be used for evaluation to lend credence to a particular assistive robotic technology from a clinician's perspective? In this paper, we survey several areas of assistive robotic technology in order to demonstrate domain-specific means for evaluating the performance of an assistive robot system.