I bought my Dyson DC07 vacuum in 2003 after comparing it against other $100-200 vacuums. What sold me was the root cyclone technology and the claim that I'd never have to pay $15-30 for another bag or filter.

It's a classic case of 'you get what you pay for'.
$30-50 vacuum -> carpet I would not care to lie on.
$100 vacuum -> good carpet cleaning.
$200-300 vacuum -> superb cleaning and HEPA filtration for allergies.
$350-400 Dyson -> superb cleaning, HEPA filtration, and save $30-$50/year on bags and filters (which you often can't find on store shelves after 2 years). Even if you're only considering a $100 quality vacuum, the Dyson would earn its keep after 5 years.

UPDATE 1-28-2012.  It has been 8.5 years and this Dyson still runs like new.  At $50/year in bags, that means over $400 in savings already!

Customer service: It comes with a 2-year warranty and seems to be built tough enough to last 20 years. The only caveat to this is that there is a decorative yellow piece near the handle whose spring breaks the first time you touch it. The engineers designed it with the wrong strength of spring, so it's common enough that it happens to everyone. I called customer service: 1 minute hold; very friendly voice on the other end; she explained the problem to me and got my name and address to ship me a complete replacement part. The whole thing was over in 2 minutes, and I'm very happy.

Assembly: 10 minutes (with manual). The overall design was logical except for the hose and tube attachment (see ATTACHMENTS below), for which I had to dig into the manual. Note: there's an excellent online users manual at http://www.dyson.com/opmanual/box/default.asp

Operation: The buttons were intuitive and easy to find. My only concern was that the power and canister-release buttons were too close together and next to the carrying handle, so that it's a bit too easy to turn on while carrying.

ATTACHMENTS: The trickiest part for me was juggling between the normal back-and-forth mode and switching to the hose attachments. The long rigid hose is normally inserted 2' into the flexible hose, which means that you have to pull out the rigid hose to use the attachments. I believe they have improved on this with the Dyson DC08 (canister, not upright), but these aren't available in the US yet.

The regular DC07 (yellow) comes with a stair tool, a brush tool, and a crevice tool. I found this to be enough, but would recommend getting the floor tool as well (the red model) for going under the bed.

WEIGHT: Although the back-and-forth weight at the handle is 4 lbs, the total weight is 19 lbs (8.7 kg), something I wouldn't ask my mother to carry up the stairs (though she could probably drag it step-by-step). That's the kind of fun job every guy should have. :) Note: the DC08 weighs only 5 kgs and is just a bit more powerful (330 vs 270 airwatts, with 12 cyclones instead of 8). For this reason alone it might be worthwhile to wait for the DC08.

REACH: 35' cord, 53' reach.

Cleaning quality: Awesome! You could practically eat off the carpet. Picks up every speck of dust, hair, and insect (live or dead) and traps them in the canister. There's a much-touted chart done by an independent lab at http://www.dyson.com/nav/inpageframe.asp?id=TECH/DYSONCYCLONE/PERF/PERF showing that the Dyson outperforms other types of vacuums. Personally, I've found it cleans at least as well (and is about as noisy) as another $200 vacuum.

For more info about the technology, go to http://www.dyson.com/nav/inpageframe.asp?id=TECH/DYSONCYCLONE/MENU/MENU

Emptying the dust: This part is a real beauty and is as simple as you'd find on any vacuum out there (immensely simpler than changing bags). Grab canister handle, release canister by pushing thumb button, position over trash bag, and pull the index finger trigger to open the flap at the bottom of the canister.

Update October 5, 2005
I've had the vacuum since August 2003, using it about once a week. It's still running great! No problems to report. No apparent loss in the dust filtering.

Update February 5, 2009
Vacuum STILL works, no problem!  Motor is as powerful as before.  I've washed the motor air filter a few times and cleaned out the rotating carpet brush, but haven't had to replace any parts.

Recommended: Yes

Amount Paid (US$): 400