He was fundamentally right to the point that most arguments against him fall back on religion, pseudo-religion, or "technology as a tool". The last of these is an obvious sign that one has not read his work. He didn't argue against just "modern technology". He argued against every large scale technology (technologies that could not possibly made and sustained by a single person, much less a village's group of craftsmen, such as refrigerators and computers), especially those rooted in the Industrial Revolution (which he views as the invention of the steam engine because that's where most agreed the Industrial Revolution started until recently), because they all inherently limit freedom. His definition of freedom isn't the same as society's, the System's. Freedom to him is autonomy (ultimate freedom of choice and self sufficiency in daily life as an individual or small group) and security (ultimate freedom to protect oneself and not be at risks by things outside of your control as an individual or small group). To him, freedom isn't legal "rights" and "legislation" because those are inherently part of the System, and the System molds humans into what best fits itself rather than what best fits humans because the System would collapse otherwise.
To sustain large scale technologies, the foundation of the System, freedom must be encroached upon. Factories need workers who are overseen by a manger who receives orders from a company bureaucrat who gets legislation from legislators who get standards from unelected officials and specialists, etcetera. The individual is powerless in this process. The features and standards of his refrigerator are not determined by him. The market argument can be made, but the market is a sham of phony choices. The individual must either buy a refrigerator that meets the quality standards of the bureaucrats, many if not all of which will see the same amount of use in his daily life, or enter into antiques and after market buying, leaving the function and quality of his purchase again to people he does not know and cannot control for something the System tells him is unsafe.
For a more societal example, take the automobile. At first, automobiles were introduced and appreciated as novelties. Cities, towns, and human life in general weren't built around automobiles. As technology progressed, the automobile became more affordable and adopted. With this mass adoption came a change in urban planning. Suburbs appeared, and, even in the countryside, the average man could no longer walk to work, his produce market, his place of leisure, and back home in a timely manner. The face of human life became scarred by roads and highways, and the freedoms of both automobile owners and the walker were denied. Automobile owners had to endure increasing regulations and fittings with the new infrastructure (i.e. stoplights, inspections, airbags, sensor minimums) while walkers had to endure the effects of these changes on their previous routines (i.e. crosswalks, jaywalking, drunk drivers, traffic, highways, long travel times, pollution). The automobile, on paper, seems quite fine. It lets you go from one place to another in a quality controlled environment with stored luggage, and you can listen to music while doing it. For reasons I already explained, the automobile is against freedom. All technology is like this. It starts innocuous because the System hasn't adapted to it. It ends restrictive because the System has adopted it.
My biggest gripes with Ted are his views on history, governance, and race, but those aren't /tech/-related.