is notoriously difficult to reason about (thank you Satoshi)

Note that it is difficult to reason because it is a stack-based minimalistic language. It has definitely some shortcomings, also because we wanted soft and not hard forks (I think it is safe to claim that all the 

 in script extensions is caused by that, but happy to be proven wrong about that.)

OP_IF has been one of the op-codes used in Bitcoin script since the very beginning

Real world usage came when Peter Todd proposed 

 for lightning too (though we use CSV for that - relative locktime): the lock is conditional (and the way we often express conditions in programming is with 

bitcoin

Nunchuk: OP_IF is useful, miniscript isn't just for fancy things

Scoresby

> is notoriously difficult to reason about (thank you Satoshi)

Note that it is difficult to reason because it is a stack-based minimalistic language. It has definitely some shortcomings, also because we wanted soft and not hard forks (I think it is safe to claim that all the `<xyz>VERIFY` patterns replacing `OP_NOP*` in script extensions is caused by that, but happy to be proven wrong about that.)

> OP_IF has been one of the op-codes used in Bitcoin script since the very beginning

Real world usage came when Peter Todd proposed [CLTV](https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki#escrow). It's basically what enables the `L` in `HTLC` for lightning too (though we use CSV for that - relative locktime): the lock is conditional (and the way we often express conditions in programming is with `if`).