Selected answers from the Dumb SEO Questions Facebook & G+ community.
David Gossage: I tend to have a quick summary at the top and go into more depth using people also ask examples and links to blog articles. Also, your site has translations from Wikipedia which are unlikely to be helpful.
Niclas Jönsson: David Gossage its temporary til I written a better text
Christine Hansen: As a customer, I like to read the text before considering buying the product and never the other way around. As for SEO, I don`t see a difference.
Jon Ohlsson: I would just base it on what`s working and the standard
Look at your comp and see what they did. Look at big box stores what do they do?
They have millions to put into this stuff. Just use their r&r for yourself
Buth Main: Googler John Mueller recommends do not use much text content on category pages. As Christine Hansen wrote it`d be better to place text before the products. But some types of tect content can be after products. It can be additional content that provides a little value for the visitor. For example, if you have not found a product, you can contact our manager or something like that.There is one rule, write/add/do all elements of your website for YOUR target audience (not for people).
Ammon Johns: In algorithm terms, I`d say that text which may look like an afterthought is more likely to be viewed poorly than short, punchy useful text used as a preface. But position of the text on a page is just one signal of literally a hundred or so just of the on-page signals. What you write is generally more important than where you position it, so long as both are equally visible.
Does it matter for SEO if category page text is before the products or after products? 
