Application performance tuning is a complex process that requires assembling various types of information and correlating it with source code to pinpoint the causes of performance bottlenecks. Existing performance tools don't adequately support this process in one or more dimensions. We discuss some of the critical utility and usability issues for application-level performance analysis tools in the context of two performance tools, MHSim and HPCView, that we built to support our own work on data layout and optimizing compilers. MHsim is a memory hierarchy simulator that produces source-level information not otherwise available about memory hierarchy utilization and the causes of cache conflicts. HPCView is a tool that combines data from arbitrary sets of instrumentation sources and correlates it with program source code. Both tools report their results in scope-hierarchy views of the corresponding source code and produce their output as HTML databases that can be analyzed portably and collaboratively using a commodity browser. In addition to daily use within our group, the tools are being used successfully by several code development teams in DoD and DoE laboratories.