Quality Score For SEO Includes alot of things:
Page quality (Panda iterations)
Business local citations (linkless citations)
Brand development / permeation
Domain ownership / history
Authority of inbound links
Other (still to come)
Surgical manipulation of SERP's will die a slow, timely death as Google begins to shift to, and use, a diverse range of factors to accurately assess the quality of your website websites.
This might explain why some websites we see who have built a ton of decent quality links have moved nowhere, and others, who employ a diverse range of tactics mainly geared at promoting their business online are seeing completely different results from one another.
If you were a search engine, you would likely always search for new signals to pull into the mix.
At the end of the day, the website with the best SEO will simply be the transparent business that has great value and offerings and tells people about them in a wide range of ways.