In my opinion a Dyson is not robust enough to be moved from house to house and to be in and out of van
Made that mistake same money would get an industrial vac
Like any piece of kit it all comes down to how you look after it and how you use it.
My dyson is about 4 years old and still working fine because I look after it. It has pulled out enough dry debris and fluff from a carpet even after the customer has done it for us with the latest in sebo or that huge, metal, £2k's worth of vacuum cleaner.
Now down to the point of what the customer thinks: It's not what you've got it's how you use it and my results and customer comments speak for themselves
http://www.checkatrade.com/willclean/ Not bad for someone who doesn't actually rate the sebo.
Can I also add that if you turn up using the sort of vacuum cleaner they use, then it makes them feel good that they have a piece of kit that a professional uses. No need to take the 'look what I've got that you haven't stuff.'