transfering files at 2MB/s vs 50-60MB/s is a big diffrence (gigabit or FW interface)
a 5 min copy jobs takes 2hrs on a GOOD wireless connection no interference, single client to an AP thats 2 ft away.
not only that, wireless is unstable and unsecure
wireless USB is a diffrent story but i dont think the mac air has it
also it has 2.1 bluetooth which is ok.. but 3.0 is out soon that supports 480mbit