What's the fastest way to transfer files from one Mac to another ?

Depends what you have available for interfaces on each.

You're in Mac Pro tower forum so of course just slap the drive into an open drive bay will always be the fast easy way.

Next would be Firewire. And it goes down from there. Wtih wifi at the very bottom. So some forum of sneaker-net even if you pick up an empty external drive case.

No, but you might ask other on MacBook Air forum.....

I would be surprised you dont' have a backup external TimeMachine etc and know how to use Migration Assistant - via sneaker net.

The new USB3 is great, unfortunate you can't take advantage of that.

There is your LAN and router besides wifi, no?

https://discussions.apple.com/community/notebooks/macbook_air

http://support.apple.com/kb/HT3231

http://support.apple.com/kb/HT3322

If both systems have Thunderbolt, then using a Thunderbolt cable you can accomplish fast file transfer using Target Disc Mode. Just boot the unit acting as the file server with the "T" button held down. The clinet computer will then see the Server unit as an external drive.