Yes and a thousand times yes.
Although there is the possibility to "open in new window", I think it is a very wasteful way to go to have to spawn a new window just to obtain another view of one file, both in terms of screen estate (need of 2 windows) and in terms of CPU resources (need to spawn a new process = more CPU = more electricity wasted = less battery life too !).
Furthermore, a large number of other software have this de facto standard, where it is possible to grab the top of the vertical slider to generate a separator which splits the view in two (pretty much all word processors, notepads, code editors, other pdf reader like foxit ... why not adobe's own acrobat reader ??). I seem to remember (but may be wrong) that previous versions of acrobat reader had this feature, and when I noticed the new and "improved" reader DC had lost this feature, it was to great dismay.
My particular use case is quite common too: I read scientific articles, where references are quoted in the text and listed at the end of the document, hence constantly scrolling back-and-forth between current page and bibliography is out of the question. It would be much preferable to split the screen in two, first pane onto the article, second pane below on the bibliography. Simple ? Yes. Possible ? No. Why ?
In conclusion, I definitely think this feature should be added.