I thought that the MX-4 was positioned to be less expensive than the MX-3, though? Not so in practice? The shin-etsu is good, but for the volume you get for the cost its a little on the high side, and I like a little leeway for screwing up, so that was why it hadn't made my short list.
And lapping the CPU isn't so nuts - I managed it, but it had the integrated heatspreader, not an exposed chip. I lapped my HS and my Northie CPU (but not the Pressie since I won't have any way to tell them apart otherwise) and it really made a huge difference in the way it "gripped". It was actually pretty difficult to break the surface tension between the cpu and HS when I had to remove it again when I switched out the power supply and I could see that the coverage was impeccable on both sides. I also set the tube in warm water first before applying which seems to make it more cooperative too.
Re that Compusa link - huh... I just googled it again and all the links that were sold out previously appear to have found a resupply stock - tigerdirect and zipzoomfly anyway. I must've hit a weird pocket in my timing before , though there was at least one store that did say they wouldn't be getting any more in at all. i managed to snag a tube off the OCZ gear site which should do fine for a while even including the pre-ylod PS3 I might be able to save. Still, it is definitely not being made anymore (confirmed through conversation with customer service re:shipping costs) as its officially discontinued. Maybe by the time I run out there will be some new breakthrough thing anyway.