Software vendors are unaware of how their software performs in the field. They do not know what parts of their software are used and appreciated most and have little knowledge about the behavior of the software and its environment. In this paper we present a metrics-based approach that is used by software vendors to create real-time usage reports, based on data gathered by leveraging aspect-oriented programming techniques. This approach enables software vendors to respond quickly to performance and usage changes in their service software, both at specific customers and concerning the service software in general. We show that by using this approach, vendors can make informed decisions with respect to software requirements management and maintenance. The metrics and usage reports are validated by way of a case study at a Dutch software vendor. While validation shows high potential of the approach, a successful implementation will require change management at the software vendor.