AutoCAD 2015 introduced a new system variable called Linesmoothing.  While it does eliminate the jagged on-screen lines we have dealt with for years, it unfortunately hides the fact that lines may not be orthographic and instead might be at 1 degree, or 91 degrees, etc. 

I suggest toggling Linesmoothing on and off to inspect your own or others' work.  Any lines even slightly off of 90 or 0 degrees will show with the all-too-familiar jagged lines, giving you a quick visual indicator that the lines may need some help.  I am so used to the jagged lines I just leave Linesmoothing off so I have the non-ortho warning immediately.

Notes from Cadalyst tip review R.K. McSwain: Kent's tip about Linesmoothing is spot on. I suppose a lot of people wanted to see smoother lines in AutoCAD, hence the addition of this feature. But there is certainly a place for wanting to see the jagged lines when things should be orthographic.