I have to add my two cents.

1. Deterministic & Non-Blocking Execution(--yes)

2. Not just Structured Outputs but strictly validated Inputs also("count should be a valid integer")

3. Actionable Structured Errors("")

4. Semantic Exit Codes(0 - ok, 1 - input error, 2 - critical)

5. Granular Verbosity Control(-v, -vv, -vvv)

6. Composable Structured Pipes