I received my 600sc last week and I've been having too much fun getting it set up
My server, with the default 128MB RAM, runs memtest86 (tests 1 thru 7) without any errors at all, at least over the several passes that I've done so far. I ran the tests after the machine had been up for several days straight.
What other tests are people running to smoke out any hardware problems? I tried hdparm, but since I've got only a SCSI disk, there isn't much it can do. I've built the linux kernel several times (just over 3 minutes -- sweet!) and have seen no glitches.
BTW, the "e1000" module code from Intel works fine with the onboard NIC. I didn't manage to find any standard driver in the 2.4.18 kernel that would work.