AutoCAD 2015 offers an improved graphics experience with smoother lines and accurate display of properties when creating and editing line geometry. Objects such as lines, arcs, and circles, and drawings aids like grid lines and the UCS Icon look smoother especially when drawn at an angle.
You can enable Smooth Line Display in the new Graphics Performance dialog box. This control is only for the display and does not affect plotting.
In addition to smoother line display, Complex linetypes display as you create and edit them enabling you to more easily place them. You can control this behavior with the new COMPLEXLTPREVIEW system variable.
AutoCAD 2015 also displays color, linetype, and lineweight for lines and polylines as you draw them.
Check out the AutoCAD 2015: Graphics video to see the line smoothing and other graphics improvements.