We built two Information Retrieval systems that were targeted for the TREC-6 "aspect oriented " retrieval track. The systems were built to test the usefulness of different visualizations in an interactive IR setting---in particular, an "aspect window" for the chosen task, and a 3-D visualization of document inter-relationships. We studied 24 users of the system in order to investigate: whether the systems were more effective than a control system, whether experienced users outperformed novices, whether spatial reasoning ability was a good predictor of effective use of 3-D, and whether the systems could be compared indirectly via a control system. Our results show substantial differences in user performance are related to spatial reasoning ability and to a lesser degree other traits. We also obtained markedly different results from the direct and indirect comparisons. 1 Introduction We are interested in building and evaluating high quality information retrieval and organization tools....