Although laboratory user studies are the most common method for validating the utility of information visualization systems, it may be difficult to determine if such studies accurately reflect the tasks of real users. In this paper, we describe a longitudinal real-world user evaluation of a visual and interactive Web search interface designed to support exploratory searching: theHotMap.com. Although we experienced some attrition during the course of the four-week study, the results indicate that many of the features of the system are beneficial and useful in real-world use. Although exploratory search comprised a small portion of the total search activities undertaken, the features of theHotMap.com which support query refinement and search results exploration did not interfere with the more common targeted searching tasks. As a result, most participants indicated that they found the system useful and easy to use.