CAT tools have become a fixture of professional translation over the last two decades yet are still treated with suspicion or disinterest by many freelancers. Acknowledged to contribute to consistency and speed, they can constrain and otherwise negatively affect the translation process in various ways. Surveys of professional translators and observations at the workplace suggest that there is a degree of frustration associated with the use of CAT tools and room for improvement in their usability. A recent large-scale survey of professional translators included specific items for CAT tool users about whether any features of their tools were irritating or missing. Many reported that there were and also availed themselves of the opportunity to provide detailed comments about them. More than half of the CAT tool users said that they found some features irritating, and a quantitative and qualitative analysis of their comments revealed that the most common issues concerned the complexity of the user interface and segmentation. There were some differences in the responses between freelance, institutional and commercial translators but almost none across age groups. The comments about missing features also tended to be about making the tools easier to use. The focus in the survey reported here was on identifying negative aspects of tools with a view to mitigating them and tailoring the tools more to translators’ needs. However, there is also room for research exploring the positive aspects of tools in the interests of optimising their usability and reducing cognitive friction.