The product is available here and is sold by Sunvalleytek. However, it is fulfilled by Amazon.com, meaning that Amazon Prime shipping applies. In addition, as it is "fulfilled" by Amazon.com, returns are far simpler than regular third-party sales.
The coupon code is GD7YDGLW. Notably, those buying from California will have to pay sales tax, though in our location it appears to only be $0.99.
Considering the number of ultrabooks (and the Macbook Air) that come with only a single USB 3.0 port, this is a boon to end users. However, we would caution buyers on many levels. For one, devices that draw a high amount of power -- say a USB 3.0 external hard drive -- are likely to either not work at all or work as a USB 2.0 device. We have seen this issue even with powered USB 3.0 hubs, that external drives plugged into them do not recognize the port as a USB 3.0 port, due to insufficient power.
We would therefore think that folks should rely on this for low power devices, perhaps such as a USB flash drive or a dongle for a wireless mouse.
Despite that, the reviews on Amazon.com's site are quite good, averaging 4.5 out of 5 stars. Notably, though, the reviews are averaged among ALL the products on that page (a drop down list selects the appropriate one). Delving deeper, we see the following:
Good test results and able to operate all 4 ports under a high current draw! - jjceo (jjceo@comcast . net)
Easy to install. After 2 weeks it's doing just what it's supposed to do. It works with old usb gadgets, and supports the speed of the new ones. - Suzham
Nice and compact and high in quality. Also a good price. It does what's advertised. Can't complain. Go and buy it! - Rem
Cheap. easy to install, fast, convenient. I tried several different USB devices including external hard drives (both single and RAID), card readers, web cameras - everything worked fine - Vladimir Efroimson
Given that, and give the easy return method if the device doesn't work as advertised (as a fulfilled by Amazon sale), we'd say take a chance.