Having used NetBSD for many years now, the biggest problem I see
with NetBSD is device drivers.

Can't talk to this device, no driver.  Can't talk to that device,
no driver.

Even if there is a driver it is frequently buggy.  About the only thing
that works reliably is SCSI.  Even a common ATA disk creates problems
for seemingly unrelated devices.

What would it take to create an interface that allowed linking
in drivers from FreeBSD/OpenBSD/Linux/... ?