I have just SP3'd my fourth server.
The first one went fine.
The second and third installed ok but there were iPrint issues which now
seem to have magically disappeared. Clicking on the printer info link on the
iPrint webpage would abend the server even after applying iPrntNWPCSP12b.exe
but that has now stopped happening. Don't know why.
I just applied SP3 to a fourth server (doesn't run NDPS), rebooted it and
then applied NW65OS3a and then N65NSS3a, rebooted it again and went to the
little boys room. I returned to find the following message on the screen:

ERROR: critical sectioning prevents requested FATFS operation
ERROR: critical sectioning prevents requested FATFS operation

I could do nothing but reset the server.
The server boots up ok now and seems fine but when I load LDNCS.NCF it sits
there trying to join the cluster for about five minutes before giving the
following errors:

2-08-2005 10:37:00 am: COMN-3.22-34 [nmID=60010]
NSS-2.70-5005: Volume PENGUIN/SYS user data write
(20204(zio.c[2201])) to block 205242(file block 0)(ZID 2267100) failed.

2-08-2005 10:37:00 am: COMN-3.22-1092 [nmID=A0025]
NSS-3.00-5001: Pool PENGUIN/SYS is being deactivated.
An I/O error (20204(zio.c[2179])) at block 1617636(file block 6951)(ZID
has compromised pool integrity.

2-08-2005 10:37:00 am: DS-10551.78-266
Bindery close requested by the SERVER

2-08-2005 10:37:02 am: DS-10551.78-263
Directory Services: Local database has been closed

2-08-2005 10:37:03 am: SERVER-5.70-1534 [nmID=B0013]
Device "[V651-A5-D0:0] DELL RAID Device 0:00 rev:1.0" deactivated by
driver due to device failure.

Something has broken my SYS volume. I'll run NSS verifies and so on but I've
done them before so I don't hold out much hope, admittedly that was a long
time ago.
Needless to say that what with this and the experiences of others in the
forums I'll not be service packing any more servers any time soon.
If it aint broke, don't fix it.