[londons_explore]

Non-interoperability of a journal isn't a massive downside. It just means after a system failure, you need to plug it back into the same OS first.

Obviously that needs to be enforced with some kind of "do not mount" option so it isn't accidentally used on another OS.

[orbital-decay]

For USB drives, it means that if you take it out from your work PC in a hurry, it might not be usable on your home Mac. Pretty serious I would say.