Haven’t seen it in action yet, but I believe this will really help us understand cause and effect of the optimizations we perform:

Change History tool enhancement: Charting
In the coming weeks, we will be updating the My Change History Tool to include a helpful new addition: Google Finance-like graphs that map change events to account performance metrics such as impressions and clicks. These graphs will give you greater visibility into event causality and arm you with insight into how the changes you make impact your account’s performance.