As you know, Google launched a speed report in experimental mode in Google Search Console. Since it launched I've seen numerous complaints that Google is all of a sudden reporting the site as slow when it was moderate or OK. Well, now I am seeing the reverse.
A WebmasterWorld thread has some SEOs reporting this. One saw 350 or so URLs as being reported as slow, all of a sudden, with no changes, now be reported as moderate.
I went to Search Console, picked some random profiles and you can see the bars change from slow to moderate:
I know this site was mostly reported as slow recently and now is mostly moderate and no - no changes have been made here yet.
I wouldn't stress too much about these reports but if your site takes a while to load and you can feel it, then do something.
Forum discussion at WebmasterWorld.