I've heard the IHS (Integrated Heat Spreader) on an Opteron does not contact the core well. Is this a rumor or is it true? If it is, how do I go about removing it safely?

You insert razor blade in the middle of left part of cpu, and then slice through silicon with pliers
Take a look at your pu, you'll see smal gap, about 2cm, that's were you insert blade

I used small blade from generic shaving razors, just crack the plastic on 'em and take out the razor

Do you have a pic without the plastic over it? And was the IHS making contact with the core when you removed it? I don't want to take unnecessary risks...

removing the ihs as you know makes the cpu much cooler by up to 10C with some ppl. but be vry careful with it, if u have an old proc lying around then practice on it

heres a nice guide on it,
http://forums.overclockersclub.com/?showtopic=61534
some key notes:
heating the procesor first makes this easier.
you have a GREAT chance of destroying your proceser.
DO NOT do this if you have a heavy heatsink like the xp-90c
this is for the person that is a DIE HARD overclocker, chances are if you dont know every tweak you wont benifit much.

so to sum it all up:
if you are not overclocking you DO NOT want to remove the ihs it makes a good enough contact for stock-medium overclock use.

You'll have to sand little 4 feet on the plastic that is attached to mobo in front by two screws, but that's n00b easy to do. I always put heatsink on cpu and then take it out and look underneath cooler to see if thermal compund is on it, if it is, then contact between cpu's core and heatsink is good. And iI always lap both the cpu core and heatsink.

What's that black goo around the core?