This document summarizes Greg Heo's presentation on profiling and performance for iOS apps. It begins with a survey showing most developers use Instruments' Leaks tool but few use its time profiling. It then discusses reasons to and not to profile an app, emphasizing the need to measure and optimize bottlenecks. The document outlines tips for using Instruments like hiding system libraries and reviews its useful call tree and annotated code views. It concludes by stressing the importance of profiling before and after changes to verify performance improvements and then shipping the updated app.