I've had a fair bit of success with the SMD code in NetBSD-1.2
and a little earlier, on Sun-3 and -4 boxes. I worked around the lack
of xd/xy device support in the avaliable kernels by netbooting the
machines (diskless) just for long enough to build a custom kernel that
had the appropriate devices. Worked like a charm, booting off of
NetBSD/i386, NetBSD/hp300 [booting a Sun-4/380 from a HP 9000/320 is
kind of like towing a Mack truck with a Dodge Dart, but it works],
and even various Li**x boxes. There are some problems with the driver
for the 450/451 controllers which result in occasional timeouts, but
they haven't caused me any data loss, just occasional bizzare
slowness. 

	- Nathan