I've built a Xeon workstation, and had a lot of issues with the NVMe drive not being found by the BIOS. It would take roughly 3 reboots, before the WD SN550 would be found.
I've replaced that drive with a Crucial NVMe drive, and since I did that, the boot issue went away. Unfortunately, the Amazon return period has passed, so now I am test-driving the suspect WD SN550 drive as a secondary drive in a PCIe extension card.
With two drives in my system, I can do some comparative performance tests.The Crucial P1 M2 2280 1000GB:
I will report back with an assessment of reliability as a non-boot drive, for the SN 550. It's read-performance does seem better than the Crucial drive. As I am using the Crucial as boot and root disk, I have not been able to compare the write performance between then. The Crucial does indeed feel slower.
UPDATE 1: The SN 550 is reliably detected as a 2nd drive by linux.
UPDATE 2: Compared to a rotating drive on SATA: