it is kind of humorous having to balance regularly. I had hit a problem where statfs() call returned a { .f_bavail = 0 } which made some tool complain; funnier, the other statfs information was their expected values and one could calculate bavail correctly from them. I didn't even notice it until then. The solution unfortunately was a full fs rebalance and for some reason the rebalance tool will usually fail with some unhelpful and scary warning.

either way, my story is the same as yours. I have no troubles, I have at least ~10 daily snapshots of many subvolumes I can pull from if I accidentally: `rm -rf /usr` or something silly like that. It's a great FS and unlike ZFS, is actually upstream in the Linux kernel.