Just going to try a stream-of-consciousness thing here:
I can think of at least three advantages of a pre-revolution lifestyle:
1) Less work.
I understand that the work week and the difficulty of work increased massively when we shifted to agriculture, and hasn't gotten much better since. I believe even if you live in a first world country and work a non-physical job you at least work more hours.
2) No pandemic diseases.
Can't happen when everyone lives in small, isolated groups and you don't constantly fly sick people around the world in planes.
3) More "natural"
I understand that humans are designed to live in groups of less than 100, and that living in dense groups of thousands or even millions in the case of large cities causes stress because of this. The kind of lifestyle we lead in modern times is also highly divorced from what we evolved to do. I spend my days working in a small fabric-covered box, fixing bugs in software that will allow someone I don't know half-way around the world to accomplish some equally abstract task. Maybe people were happier about their work when jobs were less technical and abstract? I don't know, maybe this one is a bit of a stretch.
I can also think of huge disadvantages:
1) You're going to die.
Very low life expectancies and child survival rates. Warfare and violent conflicts represented an absurd proportion of all mortality in most cases, and of course there's the lack of modern medicines, clean environments, etc.
2) No modern infrastructures, amenities, or consumer goods.
I've got a house, a car, books, ipods, laptops, television, the internet, indoor plumbing, toilet paper, heating, air conditioning, fast food, eat-in restaurants, a family cottage, business trips and vacations around the world, etc.
I don't know if I could give all these up.
3) Difficult to develop culture, education, technology, science.
As someone who cares about this species at least somewhat, I can't downplay how important the neolithic and cultural revolutions were in facilitating massive leaps in the above, all of which I would say are vastly important and critical to our long-term survival.
So. Maybe I'd be open to primitivism, but it would have to be in a form that would take advantages from both systems while minimizing the disadvantages of either, if that makes any sense.
I think we ought to use knowledge and technology to actually simplify our lives and reduce our energy consumption.
I think that's what I'm trying to say too.