As typical collaboration tools, group editors allow a distributed group of human users to view and edit shared documents simultaneously over a computer network. Fast local response and timely group awareness are accepted performance metrics in group editors. In this context, a family of optimistic concurrency control algorithms, called operational transformation (OT), has been well established. However, no study has been reported previously to evaluate their performance. This paper analyzes some representative OT algorithms and reveals that the performance of OT actually depends on a number of factors. The experimental results show the extent to which current OT algorithms support synchronous and asynchronous group editing.