This post is still pretty much how I think of the salient points. I should note that the promotion of papers before they are at all available is still ongoing, and that in at least one case it has resulted in a widespread popularization of a working paper which seems not to have been published anywhere at all! The most common reason for such non-publication is that the paper failed to pass peer-review. Yet the popularizations are still available on the Internet!
Feel free to add any points I missed in my list.