Well, I've finally got both of them. It took a while because one of them was defective, and it took 11 days round trip to go through the Icy Dock RMA process. The problem I had with the defective rack was that it wouldn't easily seat a tray with a drive installed, and further that the tray that came with it wouldn't work with the other rack. The person I dealt with at Icy Dock (who was in their sales and marketing department due to a prior contact with him) indicated that the problem I had wasn't one they had previously seen with any of their beta testers, so I'm going to chalk it up to a one-off early production run thing for now.
Physically, the PCB and rack structure itself is very well constructed - when properly installed, it should not move or flex at all when installing or removing drive trays. Performance doesn't appear to be any worse than any other of the several x4 PCIe 3.0 NVMe adapters I've used. I was able to create NVMe boot drive trays for both Windows 10 and Linux Mint 20.0 Mate. Once I had the separate boot trays prepared, I could shut down, pop out a boot drive, pop in the other one, restart, and be up and running the other OS in less than 1 minute on both a clean Windows 10 Pro and clean Linux Mint install. I was able to image a clean Win10 Pro install (with only Nvidia and AMD drivers installed) from my 1TB WD SN700 NVMe over to a 512GB Samsung 970 Pro Nvme drive rack to rack in 2 minutes, 20 seconds using Macrium Free on drives at ambient temps.
I do have to say that I don't particularly care for the drive tray design at all - they should have spent a few more dollars to make them more mechanically robust. The thermal pad inside the tray is actually a necessary part of the drive mounting and retention clip mechanism, so if you change the drives in a tray a lot and wear it out you'd have to replace it (though you can easily remove it, flip it over, and reinstall it to increase its life). Further, the thermal pad is also thinner than most generic pads I've seen so I don't know if you could easily get a 3rd party replacement that would work with it (you'd have to have one of the exact thickness or it'll affect the ability of the tray to properly seat a drive in a rack). Icy Dock did indicate they have "considered" selling replacement pads in the near future so we'll see. I also noted that the drive trays seem to need to be "broken in" by installing and removing a tray with a drive installed several times in order for the tray to properly seat in the rack. However, once it began seating properly, the trays could be exchanged between the two racks I have. We'll see if that continues once Icy Dock starts selling the spare drive trays separately (which, for me, is the whole point of this exercise).
My test system is a first gen Threadripper 1950x mounted on an Asrock x399 Taichi motherboard. When both racks are installed, they both show up in the BIOS boot order (where they can be easily enabled/disabled) and also in the F11 boot override menu. YMMV here, though, as the x399 may have BIOS options not available in a non-workstation board.
Windows 10 is hot plug aware. However, it only enumerates the PCIe bus at startup so adding or ejecting an NVMe drive to/from a rack after boot requires a manual hardware refresh in Device Manager to get the drive to show up in or disappear from the system. You can do this manually at Device Manager, or there is also a Microsoft utility called
DevCon (Device Console) which is part of several different Microsoft tookits which you can use to create a shortcut to
manually refresh the hardware at will from an elevated command prompt using the command
devcon.exe rescan. I have not yet investigated the issue on Linux Mint, though I expect it won't be such an easy solution there (if it is even possible).
@BarkingGhostar , was there specifically anything else you wanted to know?