I didn't read through the last page of posts since there is just too much info, but I've had a good experience and a bad experience with shims. Just make sure that if you get a shim, that you do not get a copper one. they can conduct electricity and short out your CPU. Second, don't use a shim unless you have a clip on your HSF that is hard to get on. I used one with my copper orb and I fried my CPU because the shim kept the HSF from touching the core... so I say it depends on your HSF

What you forgot to do was spread Arctic Silver on the core of the CPU and press the heatsink down on the CPU with the shim on and see if the Arctic Silver changed at all. Then you should have used sandpaper to grind the shim down some.
My clip is very hard to get on. One reason it crushed my CPU :dead:

yup, that's exactly what I forgot to do. when I got my replacement 1.4t-bird I made sure that the HSF touched the core....