I've only had one upgrade and didn't even ask for it. Had a longhaul from MAN to KUL2 via SIN. Was in cattle class all the way to SIN (i'm 6ft 2in so it wasn't much fun...) then inexplicably as I was boarding plane from SIN to KUL2 a charming stewardess looked at my boarding pass, smiled and directed me to business class. Thumbs up to SIA! Shame it was only for the short hop...