Quite surprised so many negative reviews. Not my experience, possibly due to other hardware or software differences.I purchased the StarTech.com USB 3.0 / eSATA Dual 2.5/3.5" SATA HDD Dock with UASP, part # SDOCK2U33EB. NOTE: two drive, not 4 drive capacity. As the name states, I use both 2.5' (SSDs) and 3.5"spinning drives with it. The Amazon purchase was in March 2015, perhaps updated from earlier. I've used the dock intermittently for 7 months.I ran Windows 8.1 Pro when purchased and Windows 10 Pro now. I use a tablet as a desktop (Microsoft Surface Pro 3, normally on the Surface Pro 3 dock station for its added USB, Ethernet, DisplayPort connections). So I'm using Windows, a purchased, not home made device, with USB version 3 connections, full power, no battery. That eliminates many who had (IMO: a self-inflicted) complaints.Next, I do not leave the dock connected and on all the time. It is simply an offline backup method so why leave it on risking possible (never happened yet) malware or virus. Offline is safer.As I started pen this, I completed a 50GB copy from my internal SSD to a slower SATA 3 Gb/s spinner, I'm now copying another folder 33GB in size. Done long ago. I see transfer speeds of 15 to 86 Mbps. Windows Explorer fully reported removal of a SSD (press down on left side ejector) then insertion of a 3.5" spinner. No freezes. No need to reboot etc.I do not award full 5 stars. The industry is awash with its SATA 1, SATA II, eSATA, PCIe, NVMe protocols with unrealistic speed ratings fully not relevant but repeated by manufacturers without a heads up to the uninformed consumer. They could do better. I have purchased and returned a competitors dock that did not transfer at USB 2 speeds so yes, this is better than other HDD docks.