SInce the Thunderbolt/Firewire adapter wasn't available, and my old MBP doesn't have a Thunderbolt port, my options were rather limited for using Migration Assistant to populate my new rMBP. Fortunately I planned ahead and got the Thunderbolt/Ethernet adapter with the new Mac.
I used a Ethernet connection via Gigabit switch to my newish Time Capsule. Everything went just fine. I didn't keep track of the transfer time, but it was under 8 hours to move over 250GB of stuff. I was gone, so I don't know the exact time.
To create a new Time Capsule backup I went ahead and just did it with a wireless connection. I didn't keep track of that one either, but it ran overnight (less than 12 hours).
The new rMBP gets backed up to the TC wirelessly. I've not kept track of how long they take, but it's nothing abnormal.
Just now I did some testing. I duped a 4.6 GB file and ran a backup. Wirelessly it took Time Machine 16 minutes to run.
I changed the file's name, hooked up the ethernet cable, turned off the rMBP's WiFi, and fired up Time Machine. It took 7 minutes to finish the backup.
For grins, since I just got my Thunderbolt/Firewire adapter, I moved the same file to an external drive via FW800. It took 3 minutes, 20 seconds for the file copy.
I hooked up a USB 3.0 drive and moved the same file....1 minute, 15 seconds.
If anyone wants to send me a Thunderbolt drive, I'd be more than happy to test the speed on it too.
YMMV.
