Not only are the slope graphs elegant and minimalist, but the article about them (link) is well studied, well thought out clear and concise (despite it's length; that is, the useful information per word is high) and well written. Here is clearly an experienced pro in the field of presentation and communication whom anyone with information or data to present is well advised to read and follow.
For about 25 years, I have been trying to present data in a way that the message was clear to the observer. I was usually somewhat successful, but the slopegraphs are far more elegant. Highly recommended.