I must admit to not having been looking for this info, but what I've stumbled upon I've seen almost equally many saying they've had a great experience contacting Fanatec support. I've contacted them myself two times, the first was a great experience, the second sadly took a long time to get any reply to, but my issue was a minor so I won't hold it against them to downprioritize it.
And for the record, no my wheel has not broken down.
My experience with their support has been this;
1. I contacted them regarding the fans on my GT3 RS starting to become noisy, I got a reply the day after asking if I would be fine with replacing them myself, I said yes and a few days later I had new fans in the mail. Replacing them myself didn't even void my warranty.
2. I contacted them regarding the fact that my wheels vibration motor is constantly on unless I'm in a car and on a track (it works normally when on track), it stops if I change my Sho to 0 on the wheel.
Took a while to get a answer (and we've not fixed it yet), but can't complain about them taking some time answering this as it's a minor issue and probably down to software/firmware and nothing hardware. I'm suspecting a driver or firmware bug, but I've got the latest drivers and can't downgrade for some reason. Going to test the latest beta firmware released recently.
Anyways, this turned into a wall of text
I would keep one thing in mind regarding the reports of faulty wheels from Fanatec, and that's the fact that people who experience problems are prone to share their experiences online, those who have a wheel and no issues are less likely to go to some forum just to tell everybody how little issues they have.
Also, when buying a CSW, I recommend you go for the bundle with the base and both the formula and GT rim, because if you buy the bundle you get Premium Service Pack for all three devices for free. You can find the bundle here;
http://eu.fanatec.com/Bundles?product_id=571
With Premium Service if you have a issue with your device that will take them more than 2 business days to repair they will send you a replacement device on loan until they're done fixing your wheel. Pretty damn good if you ask me!
Edit: That's a €150 worth of premium service for free compared to buying them seperately.