When you turn Symmetry on while components are selected, Maya automatically selects the appropriate mirrored components. There is also now a HUD element that displays the current axis of symmetry when one is active.
In addition, symmetry support has been expanded to the following tools:
The new Curve Warp deformer, introduced in Maya 2016 Extension 2, lets you to quickly connect a mesh to a curve to drive a variety of deformation effects. It is similar to motion paths but offers greater customization with a more streamlined workflow. Now, the Curve warp deformer is optimized for faster performance. It also supports bezier curves and has a new Loop Closed Curves feature. See Curve Warp deformer.
You can now change the order of vertices on a polygon object using the Reorder Vertices or Transfer Vertex order commands. See Modify or transfer vertex orders.
A new Subdivision Method option in the Polygon Preferences allows you to set the default subdivision method for new polygon objects.