This is a tough question. Technology can certainly improve the length and quality of peoples' lives. However, the benefits are somewhat unevenly distributed. Middle class citizens in America may be benefiting from the same technology that is causing hardship and poverty for workers in a sweatshop in China.
I'm also not convinced that a permanent, unchanging state of happiness is necessarily the ultimate goal for the human condition. Do we really need to be happy every single second? Would it be so bad to just settle for peace of mind? What if hard physical labor makes you happy, like it does for long distance athletes?
Gilbert's discussion about artificial happiness also seems somewhat off the mark. There are drugs already that do that, but in most countries they are illegal.