What's considered quality:

search term "angelfish" (no quotes are necessary when searching, of course); Site that ranks very well (#4): breedingangelfish.info (nothing but affiliate / ads site with very poor and shallow information - I know it because I keep these fish for about 10 years)

site:breedingangelfish.info in google gives 8 results.
link:www.breedingangelfish.info in yahoo gives 85 results (select "except for this domain"), they're mostly from squidoo, hubpages and directories (NOT dmoz.org or dir.yahoo.com), not many unique domains at all.

Sites being ouranked: fins.actwin.com/species/angelfish.html , aqua-fish.net/show.php?h=angelfish (this is mine) , animals.nationalgeographic.com/animals/fish/queen-angelfish/ , angelfish.net , aquaticcommunity.com/cichlid/angelfish.php , and many informative websites.

One would ask "Hell, WHY????"

I know the answer...

1) good domain name
2) all pages available in 1-2 clicks from homepage
3) keyword stuffing - the sentence "Angelfish prefer to select their own mates and pair up on their own out of a group of angelfish" at breedingangelfish.info/angelfish-breeding.cfm - or check occurrence of "Angelfish" at "breedingangelfish.info/angelfish-diet.cfm" (it ranks #1 for 'angelfish diet' !!! - without quotes, of course)
4) a couple of targeted links

Oh, by the way... that site shows adsense ads, but has no privacy policy at all. If this basic "TOS" is ignored, then it shows what quality is that site of.

Another "pick" is that breedingangelfish.info contains some low-resolution images and I doubt they're original unlike what can be seen at other quality websites devoted to angels.

Now what to do?

Two options:

1) Try to find the "low quality" content within your website and remove it from google's index - no matter if these pages are useful for people or not, the goal is simple; to REMOVE because google says so.
2) Buy keyword-rich domains, build your own mini sites, and get a couple of links from here and there and the money will roll in.

I don't like the second option. But if the current algorithm isn't about to be changed soon, marketers and SEO's will get this sooner than one would think and the web will be full of such shallow-content websites. Then google will have to change the algorithm again or people will start using bing.

By the way, try to search 'angelfish' in bing... angelfishrestaurant.com (nothing against restaurant, but what information about fish can they offer?) and breedingangelfish.info aren't in the bing's top10. In fact bing's results aren't 100% satisfactory, but for certain phrases they're better than google's at the moment. Also for 'angelfish diet' they show fins.actwin.com/species/angelfish.html above breedingangelfish.info's zero-value page. Still, google does do a good job, but the recent algorithm change has allowed tons of poor-quality sites to outrank established websites within a blink of an eye.

This is only one search term, I haven't been trying to find some that proves that the current results are not better than previous ones. I simply picked one search term randomly.

Hopefully someone from google will read this...

On the other hand I must say that after this update I performed analysis and I've reconsidered my site (only one site has been affected - but it's actually my best site) and I keep working hard on improvements! We all can keep improving our websites in order to be ranked better than cr@p content.

I've realised that google doesn't like:

1) if two or more pages on your website share same content
2) if a page is available after making (say) 20 clicks from the homepage

To-do for every affected website:

1) Monitor which pages googlebot visits (perhaps you'll find some broken URL's or similar things - not always caused by your site)
2) Use "noindex,nofollow" meta tag where applicable - I use it for https pages for instance
3) Make sure that each URL shows unique content
4) Perform site:yoursite.tld (whatever, combine it with inurl: for instance) to find what's indexed, what's not - low-quality pages are usually listed last or are available after clicking "In order to show you the most relevant results, we have omitted some entries very similar to the..."

And... "ads above fold" is just a myth. Adsense above fold won't affect your site's rankings, there are tons of websites that prove it (I personally checked a lot of them).