After the release of Acrobat DC in April a lot of users were not satisfied with the new user inferace. The first update of Acrobat DC features also some small improvements of the user interface of Acrobat DC which allow to save some of the unnecessary mouse clicks.
The left hand pane with the icons of the navigation panes is opened automatically if the PDF contains bookmarks, attachments or digital signatures or if the PDF follows a standard (e.g. PDF/X, PDF/A). In the new version one can see directly if it’s a standard PDF (like in older Acrobat versions).
The right hand pane with the tools now remembers its state (open/closed) and opens the next document accordingly (also after a restart of the application). Unfortunately Acrobat does not remember which tool set was activ. You will have to click on the tool set for every PDF again. If the last tool set would remain activated, one could keep the right hand pane closed and would still have acccess to the tool icons in the second row of the horizontal toolbar (if these tool icons have been defined in your customized tool set). In this version closing the right hand pane makes no sense because one would have to open the pane to activate the tool set (again) wasting an other mouse click. Therefore remembering the state of the right hand pane does not really help most users in daily production because they will have to keep the pane open in order to easily (re-)activate a tool set.
Unfortunately for the left hand pane the status is not remembered. This would be helpful for users who often use the navigation panes (e.g. page thumbnails, creation of bookmarks, adding attachments, checking of tags).
Bottom line: in the new version some unnecessary mouse clicks can be saved but there ist still room for more improvements…