Thunderbolt is rated at 10Gbps. With a $30 cable, you are now essentially getting 10Gbe networking for free between two Thunderbolt equipped macs. This is a big deal. How big of a deal is this? 10Gbe networking isn't cheap. Gigabit ethernet has a max theoretical 125 Mb/s limit with real world 100-109 Mb/s.
When you first launch your networking preference, you will notice that the OS now adds a new network port. Thunderbolt Ethernet, bridging, networking. In other words, IP over Thunderbolt is now a reality.
Now, all you need to do is create a closed network.
I chosen 192.168.2.0/255.255.0.0. One will need to be the master and the other the slace.
My 15" Macbook Retina (192.168.2.2) as the master and my 2012 13" Macbook Pro as the slave (192.168.2.3).
With file-sharing on, I can access either via their Thunderbolt IP.
Then I did some copies and benchmarks.
AMAZINGLY FAST. See for yourself.
This is over the network. The 15" Macbook accessing the SSD of the 13" Macbook Pro over the network.
Real world copies. 15 large MP4 movies totalling 45GB in less than 5 minutes over AFP.
For you UNIX networking nerds, I ran iperf
Thats right, 760 plus MB/sec. Networking is only limited to the reads and writes of the drive now.
This is a game changer. The set-up.
You can read up on multiple mac bridging here.