Beta 6 brings a lot of improvements which have improving the workflow, usability, and discoverability. Many of them were created as answer of request from forum feedback. You will not need to uninstall previous versions of 123D to install Beta 6, the installer would do that automatically. Some of the features you can also watch in the What's new in Autodesk 123D Beta 6 videos here.
Some of new key features:
- Text on sketch plane
- Supported Device Printers
- SVG Export
- Additional Polyhedrons
- Named Views in Sheets
- Enhanced 2D Sketching Environment
- Solid Creation Enhancements
- Solid Editing Enhancements
- Manipulator Look Enhancements
For more detailed description visit: Autodesk 123D