During this update, Google has temporarily stopped updating the existing reports. The Googler said:
We are making some changes to the algorithms and pipeline behind the site performance feature and so had stopped updating it for a bit. We'll resume the updates soon, hopefully within a day or two. Do stay tuned and keep giving us feedback.
One new feature I am expecting is a trustworthy indicator to be added to the tool. I also suspect the tool to update more frequently and possibly offer better explanations of what can be improved.
Forum discussion at Google Webmaster Help.