I think it varies by technology and circumstance. In my experience living and working with different levels of technology…
Living without running water is really no biggie, if you can get water delivered to your house. There is nothing you can do with a sink that you can’t do basically as well with a bucket. The only part I can think of that really sucks is washing clothes, but even that’s no a huge deal. That said, life without running water sucks a lot if you have to walk five miles to get to water. And if you do have water, you really start missing having hot water. Hot water is awesome. It doesn’t really make life much happier, but it’s much more comfortable.
Life without a car is great if you don’t regularly need to get places you can only reach by car. You get lots of sunshine, fresh air, meet the neighbors and stay a little active. But once the people around you start getting cars, you’re eventually going to hate life without one as the community changes. I think we’d all be happier if we didn’t have to drive anywhere, but that’s not realistic for a modern society.
Electricity is a mixed bag. It’s not actually as big of a deal as you’d think it’d be, but there are little things (like a fan in the summer), that you do miss on a daily basis. That said, not having electricity makes it very easy to build your social life, and very easy to your full eight hours of sleep. And it’s amazing how much better life is when you are never, ever tired. It’s like being a different person.
Cell phones are universally awesome. The internet, IMHO, less so. The absolute best years of my life were when I had limited internet access. It’s amazing how productive you can be when you are so undistracted. I think the internet is good for looking things up and sharing resources, but wasting time on forums and the like probably doesn’t make you happier.
Kitchen and household technology is also a mixed bag. One one hand, it frees up a lot of time, especially for women. On the other hand, there was a time (and still are places) when even middle class families could afford household help, and there was a whole economy around that. Now, a lot more women are expected to do it all themselves.
In the end, I don’t think life with low technology is actually all that awesomely different than the high tech life. Ultimately, what we all focus on most is our family, our work, and our spiritual or ethical life. Technology is mostly an aside to what really fuels us. That said, now and then a bit of technology is truly transformative to a person’s life. But usually it’s not the major factor in how happy you are.