Our clients are using inline-edit quite heavily, it saves a lot of time and feels also way better than pressing "Edit" to get in the full edit mode all the time.
Is there a similar functionality existing or planned also for Lightning?
If not, I would advocate to provide a functionality like that again - at least for desktop usage. But also for mobile scenarios it would be very handy (of course the current Aloha hover-pencil-display and invocation method "double-click" is not good enough for mobile cases).
To always have to switch a record between full view- and edit-mode even if you e. g. just want to fix a typo in one certain field is less comfortable. Also in SPAs it leads to updates of huge parts of the UI, possible scrolling position got lost in long tapestries and you might get a disruptive feeling. So I am sure: inline editing was great and would be great in the future.