Considering the "no addiction" guarantee, it's hard for me to see the downside. I like sleeping, and a vacation in which I could spend >10 hours/day sleeping sounds nice, but sleep doesn't lead to friendship, or knowledge, or novelty, or any of that other stuff that people typically state that wireheading lacks. Since I don't consider the happiness caused by sleeping to be bad or fake, there's no real reason why I should reject wire-headed bliss as fake. (This is assuming that I don't have important stuff to do, and wireheading isn't dangerous to me.) The main reasons to reject it seem to be rejecting it as a permanent state.