It's been suggested already in a review but I'd like to reiterate that it would be nice for layout of the editor buttons to be responsive rather than continuing beyond the intended width of the page. It's particularily bad when editing when plain text as it stacks the editing buttons vertically.
Secondly, it would be far nicer if the save and cancel buttons were styled the same as the update button (input#publish) in the standard editor page. Otherwise, the GUI feels more alien than it should.
Thirdly, the sticky save/cancel div (.wpined-control) would work a lot better at 100% width.
All of this aside, thank you for your time and support in developing a fantastic plugin that ultimately functions as required and described.