We've just released "Annotations" 🎉 🎉
You can now annotate the graphs in the "Performance" tab to mark important events in your AdWords account, eg. Client website went down, conversion tracking fixed, trying out new bid strategy... We'll also automatically generate annotations based on your AdWords change history and on your activity in Opteo.
It's helpful to annotate your changes to later help yourself make sense of any fluctuations in your performance data. (It's also useful to have notes when you need to explain to a client what you've been doing.)
You can always find all of your notes, organized in chronological order, in the new "Annotations" tab.