I have been waiting a long time for  for this product to launch.  I have been accumulating USB 3.0 drives (Western Digital Passports), but was only able to link them to my iMac through USB 2.0 connections, this not really able to take advantage of the USB 3.0 speed.

My new dock arrived yesterday and I have been able to do some speed tests.  For the test, I used the following:

1. iMac with 3.7 GHz Intel Core i7 with 16 GB RAM

2. USB 3.0 Western Digital Passport drives or in the case of the Thunderbolt drives (6 TB Western Digital My Book Thunderbolt Duo set to RAID 0).  The Thunderbolt Duo drives were connected to the Thunderbolt port of the iMac.

3. Belkins Thunderbolt Express Dock that has 3 USB 3.0 ports and a FW 800 port, plus several other ports.

4. Belkins SuperSpeed USB 3.0 4-Port Hub  

5. An old USB 2.0 Belkin Hub

6. My test file was a 55.22 GB Aperture library

Test 1: Move the Aperture Llibrary form a USB 3.0 drive on a USB 2.0 hub to another USB 3.0 drive also on a USB 2.0 hub.  It took 69 min/53 seconds for a transfer rate of 0.79GB/min or 13.17 MB/sec

Test 1:  Move the Aperture library from a USB 3.0 drive connected to a USB 2.0 Hub to a USB 3.0 drive connected to Thunderbolt Express Dock.  It took 44 min/16 seconds for a transfer rate of 1.24 GB/min or 20.8 MB/sec

Test 2: Move the Aperture library from one USB 3.0 drive to another USB 3.0 drive, both connected to the Thunderbolt Express Dock.  It took 20 min/29 seconds for a transfer rate of 2.7 GB/min or 44.9 MB/sec.

Test 3: Move the Aperture library from a USB 3.0 drive connected to the Thunderbolt Express Dock to the My Book Thunderbolt Duo drive.  It took 15 min/37 seconds for a transfer rate 3.53 GB/min or 58.9 MB/sec.

Test 4: Move the Aperture library from one Thunderbolt Duo to another Thunderbolt Duo.     It took 9 min/1 sec for a transfer rate 6.12 GB/min or 102 MB/sec.

My conclusion is that the USB 3.0 Thunderbolt Express Dock definitely improves the transfer speeds between USB 3.0 drives as compared to a USB 2.0 hub, but it is not the huge leap forward I had anticipated.  The pure USB 3.0 solution is about 3.4 times faster than USB 2.0 hubs connected to USB 3.0 drives whereas Thunderbolt to Thunderbolt transfer is 7.75 times faster.