- Multitouch gestures (3 fingers move window, 4 finger show dock)
- 2 finger scroll (You have to enable it via Mouse settings)
- Unity/Compiz 3D effects
- Webcam (just install "Cheese" via Ubuntu Center)
- Standby/Wake up
- Keyboard backlight, audio, brightness regulation
Unfortunatly one big feature of the MBA is the precise and responsive Multitouch Track Pad. Ubuntu support several features via uTouch, but the rest of the ecosystem is not so ready (e.g You need Touchégg emulation or some other hackish tools to bind the multitouch gestures inside the apps, and 2 finger scrolling is not enabled by default).
Applications like the web browser Chrome run as smooth as osx at the benchmarks, the unique difference is that the video driver provided by Linux doesn't support WebGL.
How to make a bootable LiveUSB for Mac/EFI
You need to download an ubuntu .iso image with the suffix "+mac" (example 64-bit Mac (AMD64) desktop CD)
Then You need an USB key (at least 1gb) to generate the Live USB system (Here is a tutorial)
Many Mac-specific tweaks are already provided by +mac Ubuntu versions, but are also available some all-in-one common settings via some sh script You can find in Ubuntu Forums.