Good real time groupware products are hard to develop, in part because evaluating their support for basic teamwork activities is difficult and costly. To address this problem, we are developing discount evaluation methods that look for groupware-specific usability problems. In a previous paper, we detailed a new set of usability heuristics that evaluators can use to inspect shared workspace groupware to see how they support teamwork. We wanted to determine whether the new heuristics could be integrated into a low-cost methodology that parallels Nielsen's traditional heuristic evaluation (HE). To this end, we examined 27 evaluations of two shared workspace groupware systems and analysed the inspectors' relative performance and variability. Similar to Nielsen's findings for traditional HE, individual inspectors discovered about a fifth of the total known teamwork problems, and that there was only modest overlap in the problems they found. Groups of three to five inspector...