Experts Exchange is a favorite whipping boy here lately (and with great reason). I bring it up because if Google put as much weight on the UX measurements as you claim, SERPs would be bereft of Experts Exchange links. Most of us here know you can see the answers by scrolling to the bottom, but even a lot of professional devs I know hit the back button when they see the "join now" links, let alone the novices and hobbyists.
A few friends of mine in the eCommerce business hit top 3 rankings on semi-competitive keyphrases by doing nothing to their sites but building rich internal link structures.
One of them sold ipod covers, for example. Product descriptions, marketing text, etc, all read "[iPod covers], also called [iPod Jackets] are [covers for the iPod]" etc etc etc. And each of those phrases link back to the Index.
After they did this-- creating thousands of links leading back to the index-- they went from google obscurity to top of the rankings. And they've held that spot for a long time.
And this massive amount of text with every 3rd word a link back to the index is not good content. It's horrible, actually. And there's a LOT of it.
And that's not blackhat. That's 100% legit SEO!