The recommendation for ECC memory is simply because you can't be totally sure stuff won't go corrupt with only the safety measures of a checksummed CoW filesystem; if the data can silently go corrupt in memory the data could still go bad before getting written out to disk or while sitting in the read cache. I wouldn't really say that's a downside of those filesystems, rather it's simply a requirement if you really care about preventing data corruption. Even without ECC memory they're still far less susceptible to data loss than conventional filesystems.

I've been using BTRFS for years without issue, albeit with the standard c raid modes and not 5/6.

It saved my ass when a power supply issue popped up, causing my array's hard drives to randomly drop out when reading/writing data. Managed to recover all data just fine, although it did take a while

I've been using btrfs for years, and I'd swear I've had fewer problems with it than ext4. I've never experienced any sort of data loss as a result of the fs.

I'm really interested to play with bcachefs; evolution and competition is a great thing, and it'd be nice to have a reliable RAID5 built in. While I normally prefer Unix-philosophy tooling, needing layers of different tools to get an FS working is an exception that has caused me trouble in the past, so I'm all for a batteries-included solution.

The proof in the pudding, for me, will be how easy or hard it is to administer. Messing with the fs tooling is something I do only rarely, so ease-of-use has a lot of value to me. This is why I don't prefer ZFS; the btrfs tooling seems more intuitive.

The arguments about data loss today are simply ridiculous and fallacious. They made sense in the beginning (or for raid5/6 until recently), but those who lost data were solely at fault for ignoring the warnings; yet instead of taking responsibility for their actions, they joined the horde of haters.