For me -- I haven't had one of these devices, I've just been considering getting one -- the problem isn't so much that design problems happen, or that manufacturing problems happen. While undesirable, it's how our world works currently. And I have no idea what the %%'s are, or whether Apple have higher or lower failure rates than anyone else. What concerns me is how they deal with the problems once they do occur. And how they have designed a laptop where it's more or less impossible to repair or replace the keyboard without replacing half the casing. I've had many PC laptops through the years, and while none of them were design miracles, I also don't remember having or hearing about any issues that would stop you from using the device for days or weeks while it gets repaired and the repairs costing up to half of a new device. This is the main issue for me.
Now I do suspect that the whole issue is probably way overstated by users, and especially so in forums like this one. I also suspect that the issue is understated by Apple. They must have known about the potential of these issues for at least 18 months now. That's a pretty long time to not do anything about it. Not fix the design or manufacturing defect, but also not acknowledging the problem. But they seem to be doing the right thing now, so that's good.
I would have to argue that PC manufactures are no better at dealing with issues and part failures. Also, unless you've pursed the Lenovo/Dell/HP next business day onsite warranty, say goodbye to your PC for weeks as you'll have to ship it to the depot for repair. I'm not standing up for Apple, but I do think the ownership of issues, and time to service, etc, is pretty equal between PC manufactures and Apple, with the some PC's manufactures being notably worse.
As for Apple knowing before hand about the issue, they probably did. But it's Apple... their ego walks into the room first, and design fault? What design fault?...