From USENIX LISA 2010, San Jose. Visualizations that include heat maps can be an effective way to present performance data: I/O latency, resource utilization, and more. Patterns can emerge that would be difficult to notice from columns of numbers or line graphs, which are revealing previously unknown behavior. These visualizations are used in a product as a replacement for traditional metrics such as %CPU and are allowing end users to identify more issues much more easily (and some issues are becoming nearly impossible to identify with tools such as vmstat(1)). This talk covers what has been learned, crazy heat map discoveries, and thoughts for future applications beyond performance analysis.