The changes that were merged for Mir 0.1.2 mostly come down to bug-fixes, but there's also other happenings. Mir 0.1.2 has:
- Resize support for client surfaces (resizable windows on Mir).
- ARM Mali T604 driver support hooks from Android (on the Google Nexus 10)
- Various Android driver support improvements.
- Mir "surfaces" have been renamed to "scene".
- API clean-ups and changes.
- Updated documentation for the new "ubuntu-desktop-mir" package.
- A new display that renders its output to offscreen buffers.
- Performance regression fixes.
- Client input receiver support.
- A udev wrapper for dealing with input device detection.
- The ABI has been bumped on libmirserver and it's now at version 11.
More details on the changes can be found via the Mir 0.1.2 merge in its Bazaar code repository.