I wouldn't want to be a wirehead. I do things like exercise to keep my mood up now but I think of it terms of wanting to be productive rather than happy. (I find that exercise, health and regular sleep/wake cycles are essential for this.) If you could wire me up to be smarter and more productive (intellectually), but the cost was chronic pain, I'd probably sign up for that. (I can't really imagine how you could reconcile higher productivity with chronic pain though; the experience of pain seems to necessarily involve restricted attention.)