This is a mixed review. Purely as a vacuum, I give it 4 stars. Reliability... 2 stars.
I used it for 2 years in a 900 sq ft apartment, carpet and hardwood, with a fuzzy cat. It has great suction power, is very easy to maneuver, lightweight, and being bagless, cost-free maintenance. It made me enjoy vacuuming. Now in a small house for a year, I realize it doesn't have enough range due to battery life, but I can't complain - that's not what it was designed for.
My biggest gripe is with its reliability:
1. The small bearings in the power brush overheat and melt the plastic spindles they rub against. Through many melt/cool cycles, the head will eventually stop turning or the belt will burn up. I've had to disassemble the head on 3 occasions to reshape the bearing housings.
2. The electrical wires for the power head snake through the swivel joint. Over time, the wires will eventually shred. The first time, I re-insulated and soldered the wires back together. When it happened a second time, it was clearly a design fault. I've drilled holes and routed the wiring on the outside to bypass the swivel joint. No chance of failure now =)
3. Not so much an issue of reliability, but more of inconvenience, the cyclone doesn't deal well with my wife's long hair - its regular maintenance to go through the red canister piece with a pair of scissors.
4. The above holds true for my parents - they received a free replacement while it was under warranty, but I do the repairs now. My sister should have consulted me before buying.
Apart from the above woes, this piece of hardware has made vacuuming enjoyable for me. I do it more frequently and feel good about having a clean house. I still plan to use the stick vacuum to gather up kitty litter, but with new needs and hours of reading reviews, I'm on my to pick up a Miele S4 this afternoon. Happy vacuuming!