I'd rather not be wired up and given drugs for happiness, although technically I have tried ketamine + TMS, which is kinda similar.
The thing that I would worry about most if wireheading existed is that the brain isn't built for eternal bliss. There's a thing called the hedonic set point. For the lack of a better description, the hedonic set point basically selects for a life consisting mostly of striving. Evolution doesn't really have a "why," but it's a reasonable guess to say that creatures who strive are willing to fight for the best food, territory, etc., and sometimes they win. Like pro athletes who "stay a little bit hungry" no matter how successful they get. If all your desires are completely sated, you lie there like a body on a slab, which is not a very sound reproductive strategy.
The hedonic set point keeps you "a little bit hungry" by always setting enduring bliss just beyond your reach. Your brain actually develops a tolerance to endorphins, and begins to demand greater and greater rewards to get the same effect. That's exactly how addictions work, actually. It's not literally the drug or the sex or whatever that is telling you "more, even more, even more than that," it's your own pleasure/reward system.
Some longtime addicts get to the point that there aren't enough drugs in the world to make them feel good. Their reward systems have given up the ghost, and it no longer matters if they're on drugs or not. They feel like shit regardless. Often the brain eventually heals, but sometimes it doesn't. Opiate addicts are especially vulnerable to their drug of choice blowing up their reward systems permanently. They feel like shit forever, like many of us. And like many of us, they shuffle onto that bus. There's nothing else for them to do.
All animals (afaik) have hedonic set points. Even in the more-realistic type of sci-fi, you couldn't reverse-engineer yourself into a lizard or something and beat the hedonic set point. If a thing has a reward system, it probably has a set point.
Trying to hack your brain is a terrible idea. Says the guy who was put on antidepressants as a teenager & is still on them 30+ years later.
Edit: Turns out there's reason @FuneralCry and some of you others don't like existing. Also why "heaven" makes zero sense to me.