I got around to pulling apart my rig last night to move it to AS. The heatsink was quite flat -- I was surprised by that as most heatsinks I've run across required lapping. The P4 heat spreader was another thing altogether. I wet lapped it successively with 400, 600, 1000, and 2000 grit sandpaper. Removed much of the silver coating by doing this (flat copper is much
better than non-flat silver). Then blew some compressed air over the little hole and a bit of moisture exited around the PCB -- so I cleaned that up. It's good that it wasn't air tight as I didn't want to wait around after lapping to put stuff back together. Applied a very thin layer of AS with a saran-wrapped finger to both the heatsink and CPU, then dropped them into my system and gave it the smoke test. Success -- no smoke escaped the system
Temps running same as before, but with a much
better cycle time on the fan (i.e., off for longer, on period shorter as well).