Selected answers from the Dumb SEO Questions Facebook & G+ community.
Jody Nesbitt: yes, its a dup content issue, see here https://webmasters.googleblog.com/2010/04/to-slash-or-not-to-slash.html
Neil Cheesman: I read that a short while ago... it also says "Rest assured that for your root URL specifically, http://example.com is equivalent to http://example.com/ and can’t be redirected even if you’re Chuck Norris."
Steve Wiideman: It`s on our list, but not as high of a priority as great content; canonical tags are a great hint to SEs, if replacing internal links is too much of an effort.