Dysons are good, and if you are comparing it with the rest of the (frankly very poor) market, then actually worth the double price tag when compared to Vax, Hoover, Electrolux et al.If you're going down the upright road from your local Argos or Currys, you wont go massively far wrong with one. Yes, they aren't quite the pinnacle of reliability but they'll 1/10 outlast said cheaper fair, have a 5 year guarantee as standard and the Dyson after Sales Service is actually very good. If money is a bit tight at the moment, pop into a second hand charity shop and pick up a second hand one, the odds are it'll still go, and as long as you haven't paid much over £50 for it, once a year at least Dyson run a money-off trade in through the retailers (normally just before new-model launch time), and the trade in value is often £50-£100, so - profit! I've had 5 Dysons in my past. None of them have ever "died", they've just assumed different jobs; the DC04 of late 90 vintage still runs, its just been relegated to the garage for car duty.
Having said allll that, if you were looking maybe at a cylinder vacuum and weren't to fussed with the bag/bagless thing, then +1billion for the Henry. Bombproof, almost literally. I've see them used - sans bag as well - to clean up a house after a remodel before, masonry dust, wood chippings, metal shavings, the works. its just swallowed the lot up and that red face just kept smiling. Absurd. Incidently, use without the bag isn't recommended, and neither is near industrial level cleaning, but it just goes to show their robustness.
Can't say a lot about Sebos personally, but I've known quite a few one-man-one-van contract cleaners down the years, and most will either say Numatic (Henry), or Sebo.
