UPDATE 06/02/13: Haswell just launched, and it looks like Intel did not change the manufacturing process of the thermal paste. Haswell still uses paste instead of solder between the IHS and die. The CPU in the video is an Ivy Bridge, but the delidding of Haswell still applies.
00:15 - temps before mod
02:24 - removing the IHS
10:02 - cleaning old stock thermal paste
12:56 - cleaning sealant glue
15:54 - applying new thermal paste
17:27 - installation into motherboard
20:27 - concluding temp results
Intro and background: With this generation of Intel processors, Intel decided to cut corners and use very cheap TIM (thermal interface material) between the bare CPU die and the top IHS (integrated heat spreader). Cheap TIM does not transfer heat away from the die well, that's why Ivy Bridge processor heat up very fast, especially when overclocking. With Sandy Bridge and earlier CPU's, Intel used fluxless soldering between the CPU die and the IHS, so they do not have this problem.
By taking the IHS off of Ivy Bridge processors to apply a better TIM, you can get a significant reduction in temperatures without needing additional cooling hardware. As a result from this simple mod, you may get a higher max overclock, more stable results, or reduction in fan noise for a quieter computer.
Do not try this with Sandy Bridge or earlier processor generations since they are soldered on, and much harder to remove the IHS. At the time of this video, here are all the Ivy Bridge models that this works on: