The hardly original idea behind it is that you tell it (and the world) what you are reading, watching, listening to and eating. In return, it tells you what other people consuming and, more interestingly, what you might want to try.
If this has any chance of working, and I think it has, then it must be totally painless to add and browse this site. Any friction would cause the site to be used and updated less and make it less compelling. Fortunately, the designers have shown a knack for ultra-polished, no-hassle, smart, just-works interaction. I suspect this will make it a reader2 beater.
Straight onto my essentials bookmark list.