I'd never use BA miles for free BA trips due to the fuel surcharges, which approach a discounted Y fare in magnitude (and are even higher in premium classes). If you want to use BA miles to fly AA or other OW partners, that's a different issue. I've used my AA miles for OW partner flights, but never BA due to the surcharges. Occasionally I fly BA in paid economy, but only to earn miles into AA, and I skip BA for reward travel.