I have a bit more information and trends across sites and a few clients and niches I follow.
Quality Shake Up
This update appears to be a lot of 'quality' and 'authorship' changes.
Remember google authorship? The easily gamed 'if we know who you are all your stuff ranks better' thing they had? The major trend sites I track is swinging back into the direction of 'if we know you...'. Unique about me page sites are doing quite better.
I saw a drop in sites in a few verticles (not my own) related to health. The biggest changes were fairly broad stroke. I saw other sites (with a clearly skilled SEO working on them) shake down the top ten. Onpage perfect, a few great links from huge sites, but unqualified author.
SEO Common Trends
Different link building tactics used on all sites I checked. My main approaches (shared on bhw) moved down top ten on several sites. So did PBN only sites, 301 redirect 'business buying' sites, PIN sites, etc.
Basically, every major tactic has shaken down a bit. What moved up were normally sites already doing well and 'deserved' to be higher. This is always debatable. But some sites really are superior I saw move up.
Surprise Jumps
My biggest suprises were current sites ranked 100 or worse jumping to page one.
Sites with 'bad' SEO done or spam. A couple of my test sites jumped up. On page 'perfect' but different link methods used.
My test sites using off the wall on page in large did not shoot up.
My Biggest Drops
So far three sites took a hit majorly for me. Many moved down top ten. Those that took a big hit all were:
- Selling something (affiliate or own product)
- No clear author (admin author, no profile pic or page)
- Content wasn't the best. Perfect on page and site speed, etc. But it honestly doesnt read the best and has fluff.
The slight drops had none of the three main problems. Better sites moved up.
What will I be doing?
Re - tooling some content and adding author pages.
My other note is that sites that were hit hard did not vanish from serps. They dropped back a few pages. If a kw had 10 pages of well optimized results sites moved to page 9 or 10.
That makes it look to me like a quality update - meaning google is being honest. A core update.
The spam ranking? Makes no sense.