Currently testing out unRAID and using an Intel 750 NVMe SSD (which is working well), however one limitation is that the device cannot be properly managed (i.e. firmware updates, low-level partitioning etc) due to the nvme cli utility not being present.
The utility can be found at https://github.com/linux-nvme/nvme-cli and it would be great if it could be included in unRAID in the future (as it would make working with NVMe devices significantly easier).
I know there are other bits around NVMe devices that are needed (i.e. support for reading drive temps, discard triggering etc), however those are different issues for a different day.