Honest one: the taxable presence / permanent establishment problem. I tried to roll Deel out at a previous company and employment law pushed back hard, having a senior employee operating from a country where you have no entity creates real PE exposure for the parent company, and an EOR contract doesn't make that go away on its own.
For junior contractors it's fine, but for anyone strategic the risk lands back on you. If they've genuinely cracked this since (proper structuring, indemnities that hold up, jurisdiction-specific guardrails) it's a game-changer. If not, it stays a great tool with a hard ceiling on how senior you can hire through it.