The only real pain point I have is my hard drive layout. I've got a bunch of different drive sizes that are hard to expand on without wasting space or spending a ton.
I'm on btrfs. I have a 14 TB, a 16TB, and two 7TB drives in RAID1. I'm running out of space for all my linux ISOs and I'd really like to transition to some sort of 3 or 4:1 parity raid, but you're not supposed to use that and I don't see a clear path to a ZFS pool or something