Recently, my friend decided to upgrade his system from AMD Athlon 5000+ Black Edition and GigaByte 7-Series motherboard to Core 2 Duo E8500, hopefully to run at 3.8 GHz (FSB1600). 5000+ worked hard for almost a year at 3GHz, a nice speed bump from default clocks.
Back in July, he replaced previous cooler with OCZ Vendetta, and bought Arctic Silver 5 thermal paste (high density one) for better heat transfer. Fast forward to November, and the time for upgrade has come.
Ivan decided to keep his OCZ Vendetta cooler, and we removed the motherboard from the case. This was followed by CPU cooler removal, but what we saw next was nothing short of surprising. The paste suffered from separation between silver particles and the carrier material, with the paste spread all around the cooler and the CPU, not looking nicely.

Not looking good...

Not looking good...

..not good at all. Vendetta's unique design saw paste carrier spreading all around - cleaning was almost impossible.

..not good at all. Vendetta's unique design saw paste carrier spreading all around - cleaning was close to impossible. But using Arctic Cleaner helped a great deal :-)

I’ve been using thermal paste since 1995 and my first overclocking: Intel Pentium 100 to 125 MHz (1.5×83) – but I have never seen such a separation between metal particles and the carrier. Bear in mind that I removed at least 500 coolers in the past 8 years (couple of 50+ motherboard tests will do that for ya ;) ), but I never saw such separation, even with crappiest pastes around.
Cleaning the Vendetta proved to be close to “mission impossible”, since the liquid carrier penetrated all the tiny spaces between the heat-pipes and cooler’s body. We think that this “separation” was a byproduct of Vendetta’s open design, and potential exposure to air across the surface of the CPU.
Followed this disappointment in Arctic Silver, Ivan canned the paste (after just this application) and opted for Gelid GC-1 and didn’t look back.
Now, E8500 is happily ticking away, feeding the 9800GX2 in Folding@Home and doing a lot of video transcode using Badaboom software.