Based on the really, really crappy results that google gaves me out lately
People on Hacker News seem to think Google's results have gotten worse over time. Maybe they have for the narrow set of interests and requirements of this crowd, but I'm very confident they've gotten better for the vast majority of other users (users who I bet are less likely to use an ad blocker too).
That they eliminate all SEO crap (i dont want those results anywhere near the 100th page of results) and ads from my results and serve me relevant content.
This is an extremely difficult engineering problem. Google doesn't make a conscious decision to include low/middling quality SEO'd content. That content is optimized to appear relevant and high quality. Google does a better job than say Bing at telling the difference, but it's still obviously an unsolved problem.