I adore Lightning and am very happy to see a UI interface update coming in Winter 18.  However, I am still concerned as to the speed of this UI.  It's definitely much slower than Classic and though I have most of my users in LEX - they complain constantly that it is buggy and sluggish.  Do we know if this is going to be rectified? I explain that this is a UI in development but I am fast running out of excuses and somewhat surprised that this has not been addressed yet by the developers of Lighting after two years.  SF want adoption to LEX but this is the biggest negative of the system.