In this video you can see a comprehensive review of the modeling improvements available with Maya 2018 made by Maya Modeling Product Designer Trevor Adams.
The video does not contain audio, but the text explains the features very well:
These are just a few new features the author demonstrates:
- More Primitives are added
- Super Shapes introduced
- Merge components to center is added
- Quad draw in a new tools section
- Speed settings for MMB-Dragging
- Double-click vertex to select all vertices of a geometric shell
- MMB to drag-tweak components with active transform tools
- Rotate and scale group selections of components with MMB-dragging
- Shift + Drag to create copies of instances
- Muti-Cut supports snapping
- Vector Displacement Maps added to the Sculpting Stamp Library
- Topological Symmetry is added to all sculpting tools, you can use symmetry for asymmetrically-posed models (awesome…!)
- … and many more.
The improvements are amazing, check them out.