Several months ago I wrote about how I've seen lots of issues with disk corruption and multiprocessor lockups with DS20L and DS25 Alpha systems.
I can happily say that the systems are completely stable and happy so long as the motherboard ethernet is not used at all.
I got a system up and running on an IDE disk and had it compile for two months with a multiprocessing kernel without any problems. I'm now running with an SSD on the SCSI bus, also entirely happily.
There is one problem, though, that I can't seem to figure out. Sometimes, the machine boots in a state where the time drifts several seconds per minute and the times reported in top are "???". This doesn't seem to impede the system in any other way. I haven't yet figured out why it happens.
So, in case this helps anyone else, I'm putting it here: until someone fixes the problems with motherboard ethernet on these systems, just don't use motherboard ethernet :)