I just crushed the edge of my Tbird core when taking off my air cooler to put on my waterblock. it was because of the poor design of the clip on the heatsink. it was the toughest one i've ever taken off, and i ruined my new 1.2Ghz Tbird. i wish i woulda just waited for my waterblock to come in, but that's hard to do when you have a bunch of new pieces parts ready to go. ....... that would probably prevented me from buying a temporary, hard to remove, heatsink and fan (CYBERCOOLER ..... the all copper one). ...... the waterblock i have, a maze2, is nice and easy to get on flat. so, i won't get a shim this time either. i've only broken this one thing in my years of building computers for myself and others. ...... but ...... a shim woulda saved me from buying a new cpu.......... if you have the time to get a shim and you are worried about having one or not, go ahead and get one for a little piece of mind. just don't treat your cpu like it can't be broken. treat it like you would if you didn't have any extra security. maybe then you won't end up biting the bullet like me.