There are dozens of new features and enhancements between 0.28.6 and 0.28.9.
A complete list of changes can be found at https://www.klayout.de/development.html

• Open a few GDS and OAS files (kB to GB in size) and browse the layout.
• Open Help->About and check it ruby/python bindings are present in the Build options and ~20 .so files are present in Binary Extensions.
• Start python3, import klayout and pya modules.