That is one of the great things about mobile devices. They do strip away all of the extra things that can steal your focus. I was also surprised by the findings of that study. I would have thought just as you did, that comprehension would drop on tablets and e-readers. I'm not sure why I thought that though. I own a Kindle and I wouldn't say that I have understood less any of the books that I have read on it as compared to the physical books that I have read. I wonder why that perception is there? Is it just because print texts are our preference? As a teacher though, I'm glad to know that there is no difference in comprehension levels.