My best performing sites, which have survived Panda, Penguin and manual unnatural link warnings, all heavily utilized the primary keyword(s) in the anchors. However, I'm exceeding 200-300 exact match keyword variants to achieve these results. It works extremely well when combined with good onpage SEO.
I am seeing this as well.
I think one of the biggest misconception surrounding Google's over optimization is the exact match anchor text. So, everyone is scrambling to dilute their exact match anchor text with generic. In a sense, is a good idea to make it more natural, but not as necessary as most may think.
I think Google's agenda is to stop webmasters from targeting a few keywords in their anchors. It's not natural if you have 10,000 links and only using a few keywords for anchor text. If you have hundreds of keyword variations you should be fine.
I personally use as many keyword variations I can think of, raw urls and some generic. I try not to use "click here", it is a dead giveaway.