Do you have source for that? I can't find any reports of widespread problems.

The speed wasn't the part I was impressed with, it was the ability to do in place upgrade of a filesystem on millions of devices without any massive amounts of problems.

I find that to be a tour de force.

While I'd prefer new filesystems to be faster than older ones, I understand that improvements don't always come in the speed dimension: it can also come in the integrity/data loss one.

You can run your filesystem without write ordering, cache enabled, and no-op for SYNC/FLUSH, and it will be very fast, but you will risk data loss.

It seems reasonable to me to trade speed for integrity.