Earlier, we mentioned that the Elgato dock's USB ports are rated to 5GB/s, and that they support UASP. Making use of the latter requires that a connected device also supports that protocol. To test this I used a StarTech S2510BPU33 drive enclosure, into which I installed a Samsung 840 Evo SSD.
When I tested this drive with Macs that had a built-in, UASP-compliant USB 3.0 ports (a 2012 Mac mini and a 2013 MacBook Pro with Retina display) it achieved peak transfer rates of 437.4MB/s when reading data, and 416.9MB/s when writing. The drive's median transfer rates held up well at 347.2MB/s and 364.5MB/second, respectively.
A different picture emerged when the drive was connected to the dock. In that configuration, the best 'read' speed the drive was able to reach was 351.2MB/s. Its peak 'write' speed suffered a much greater reduction to 272.6MB/second. Correspondingly, the median read, and write speeds were reduced to 292.1MB/s and 228.8MB/s.
To verify these results, I tested the drive on the dock's other two USB ports, which demonstrated no difference. The positive is that the drive stayed close to these peak transfer rates during our large file tests – the medians are dragged down when transferring small files, which we expected.
This limitation dents the dock's appeal as a way to increase the number of USB 3.0 ports on a Mac that's already equipped with USB 3.0. However, it is a better but more costly option than a USB 3.0 hub because Thunderbolt's greater bandwidth means less contention.
No software needs to be installed on a Mac to use the dock. Its USB ports and a connected display are instantly available, and its headphone and microphone ports become available as options in the Mac's Sound preferences pane.
It's worth visiting Elgato's website to get an optional download. It unlocks a high-power mode for the dock's USB ports, enabling them to charge more demanding devices. This means you can simultaneously charge two iPads with Retina display and an iPhone through the dock.
The download has extra value when used with a MacBook because it installs a utility into the menu bar, which enables you to eject all connected devices at once. The dock also works with Windows 8.1 after you download and install drivers for its USB and Ethernet ports.
It's important that you don't mistake the presence of a HDMI port and the ability to connect a Mini DisplayPort adaptor into the dock's second Thunderbolt port as a way to increase the number of displays that can be connected to your computer. A Thunderbolt port carries video and audio to a single display alongside data going to other devices. If you try to connect two displays to the dock, the one attached to the HDMI port is active and the other is ignored.