You can boot straight into snapshot, may be useful if an update went wrong or you don’t like new kde.

You can change drives and raid configuration online. For example I bought a laptop that had windows preinstalled, so I used the second half of the disk space for linux, then I figured I don’t need windows so I formatted windows partition to btrfs, added it as a new device, moved all the data there, deleted the old linux partition and extended the new one to the whole drive, all that easy and without reboot.

I’d be looking into setting up ZFS on root for my next machine

I too was on the path of adventure once but then the kernel module hasn’t been built after the upgrade. Also btrfs offers some nice features for root especially that zfs doesn’t have.

Probably wouldn’t work as GPL license was published much later in 1989.

Probably means modern high speed trains. Most of them run in China so yeah they likely use Linux.

Do most of the trains in the world use Linux? Sadly no, they probably use coal.