I know that I'm not the only one that has visited websites where the copy is very unnatural to read. Its just a paragraph that is stuffed with keywords and I consider it a mild form of spam. I personally don’t think that is difficult to write for humans and search engines. It just takes more time and thought. They can both be achieved without one compromising the other. Some people believe that you should write for humans and let things fall into place, people will find your content and link to it (a main ingredient of SEO). While this can be true, incoming links are only part of the equation. The more on page optimization you do, the less off page optimization you have to do to rank well.
Don't become obsessed with Google and forget your human readers. Keep an even keeled approach. You will benefit both from search engine traffic, refferals from people who enjoyed your site experience and loyal readers who keep coming back.