The unit was used on about a 0.25 acre flat lawn, about every 10 days or so, when available.
I got a rotary brush attachment with the unit which came incomplete and bent, and was completed and unbent after about three months. There's was a front guard or shroud missing on arrival without which you needed eye protection to use it.
The belt was replaced under warranty. I have no idea why it broke. Neither did the dealer who replaced it. That alone took 3 weeks. My neighbour is a farmer, and he (seriously) suggested I wasn't using it hard enough,... go figure.
Re the carburetor, all of the above. As per the dealer's advice, I was running with premium gas. He has a "thing" about ethanol.
The main transmission failed because it blew a seal and I now have stripes of oil stain on my driveway, and lawn. The other transmission was not replaced, but the dealer has suggested it might have to be because it gets it's oil from the main transmission, and may also have been damaged. I didn't get an answer as to if he had checked it for damage, so I assume I'll be the one he thinks is going to test it. The symptoms, in addition to the oil leak deposits on my property, which, btw, I didn't observe because this evidence presented behind me, were that the machine stopped moving, either forward or backwards. There is no warning light or other indicator for this type of failure.
The machine has spent more time in the dealer's shop waiting for parts and repairs than in my possession, so much so that I had to purchase another (walk-behind) mower, which is doing terrible things to my arthritis. The dealer admits it's a lemon and worthy of a refund, and has referred me to Huskvarna. Huskvarna insists the dealer IS Huskvarna, and responsible for a refund, so I'm getting a lot of unwanted sex for my money. I've written a letter to Huskvarna Sweden asking for a refund, but am quite pessimistic about that avenue at the moment.
Good luck with yours
ttul