In a word, yes. Herman Miller chairs are significantly better quality than their competitors. They really are built to last, and provide total spinal support, following the natural alignment of the spine. They're also designed for a dynamic fit, supporting the sacrum not the lumbar (as many other chairs do). The materials that make up the chairs are strong but flexible and each chair is made of specific materials that are perfect for that particular chair. They are also designed to dissipate heat and distribute weight.
The chairs come with a 12 year warranty designed for 24 hours of use, and according to Mike Rowen, EMEA market manager - global performance seating at Herman Miller, most people don't send them back. This means Herman Miller chairs are a sustainable choice too, because you are likely to only buy one of them in your lifetime (unless you get addicted and want more!).