I did once, back in 1996 or so, redeem 450 Air Miles for a flight to Paris. This was purely because I was only getting them from credit card spend at the time and never thought I'd get enough for a decent reward.

However, the story had a happy ending. The flight was delayed for seven hours, so BA gave me all my miles back and a £200 BA Holidays voucher. I managed to use both together for a 'cash and miles' three night break to that other exciting long-haul destination - Amsterdam!