Dyson vacuums are strange. They really seem to polarise people. I think they are badly performing, fragile, expensive, and hard to repair. I can't see why people think they are more powerful or clog less easily - you start off with less power than a conventional vacuum, and it reduces more quickly than a normal vacuum! They are also very poor at filtering dust.
Also, every time you empty them, you need to be careful because half of the finer dust ends up airbourne! I much prefer removing a bag and binning it whole.
There's so many parts in them that if you need to repair one it will take a while working out what to order. Compare to a Numatic Henry, where I can call them up and describe the part (the black plastic thingamy that holds the final filter etc.) and they can send it out!
I think the reason is the high cost - and I see people do this all the time. They spend a lot of money on a product and believe it HAS to be good. It doesn't matter that it isn't, it's all in the mind. People do the same with cars as well - overlook fairly significant issues because after all, it's a BMW/VW/Mercedes...