Sorry, I don't know any meth addicts. But I think your statement may be because "like" and "need" are two different things - it's possible for the brain to need something but not find it particularly pleasurable (about a third of the smokers I know don't enjoy smoking in itself, and over 3/4ths all don't enjoy it once they factor in the cancer). Any decent job of wireheading could avoid this, though.

Wireheading is hijacking the signals that originally help our brains learn / act / adapt / etc, and just hammering on a few of them. It doesn't make sense to me to say that all life is already wireheaded, because in the beginning there was nothing to hijack.