I gave a talk at the East Coast Game Conference this year titled “Guided Content Optimization for Gears of War 3”, which went over pretty well. The slides are available here.
The talk was about the processes and tools that we developed/extended to help make Gears of War 3, covering our philosophy, memory and performance feedback loops, and some of the tools that help gather, process, or visualize performance data.
The talk was intended for a more general audience, but there are lots of UE3 specific documents on UDN that dive into more detail: