Hi,
I still had issues with the MBP retina installing the driver as it wouldn't find the lexar card reader, these may be applicable to the MBA too.
I unzipped and installed the package, the computer needed to be re-booted.
Then I went into applications and found the Lexar Firmware updater 1.00 and ran that.
This is when I came into issues as the firmware couldn't detect the reader, I pulled the USB half way out of the MBP and only then the firmware updator found a device attached. I then clicked start to update the firmware.
Now when I attach the reader the MBP regonises the reader. It's not a good way to install the driver, but thats the only way it worked, now i need to calculate the speed at which the reader works to see whether it's faster than the USB 2 version.
Hope it helps