Bought this from Woot two years ago (yes, a refurb).
Generally, just love it to pieces. Agree with folks who comment about the wand hose pulling back pretty hard--it is annoying. But not a deal-breaker for me.
"none of those explain why or claim that a ball is better or more maneuverable than any traditional well-designed vacuum."
Because the ball lets you steer it by turning the handle to one side or the other. It won't fit into a space that another vacuum won't, but you can angle it around standing in one spot. This is great for getting areas with a small opening that spreads out a little (like between by wife's large plant pots). The Dyson goes in, you twist the handle to counter-clockwise and it cleans to the left. You then twist the handle clockwise and it cleans to the right. Then you pull the vacuum out and move on.
Can't do that with regular vacuums--you have to move yourself to steer them, and the handle has to be able to pivot around to aim it. Trust me, it's great once you get used to it (it is a little different at first).
My son has 2+ foot hair. It wraps on the beater bar. It hasn't been to hard to unwrap, usually I can pull it off and unwind it, but it's like every other beater bar vac I've had. The Dyson disassembles easily for the tangled stuff, IMHO.
The Dyson is also tough on cheap rugs with glued on yarn "shag". The kind that has a long string that is looped on to the rug base, back up, and then down for a continuous run. I assume they must be cheaper to make, because, aside from the Dyson, they unravel with normal use. The pets find them amusing, but I spend a lot of time trimming off the loose ends.
Good rugs have never had a problem.
I think the Dyson works well on our hardwood floors, and with going from the rugs to floors. I'm not super picky, maybe, but I don't experience blowing debris problems.
The HEPA is amazing. I had no idea I needed that feature till I got it. The Dyson makes the air in the house cleaner smelling after I'm done vacuuming. I had no idea how much nicer it made vacuuming. Now I'm hooked.
Empty the canister when you are done. All the dust, dander, mud, hair and schmutz will join forces in the canister and molder into something that may start demanding civil rights. I just grab the kitchen trash can, go outside on the porch and dump it in. There will be a little dust during this process, so being outside is better. I wack the the side of the canister a couple times to dislodge stuck stuff as well.
Just love my Dyson. Had a Kirby, had a Eureka, had a bunch of other cheap vacs. Dyson iz da Bomb.
Fundamentalism is a crime against humanity