It's an interesting point. While I'm happy to fly the 787 short-haul within Europe, I'm also more than happy to let other pax do some flight testing for me on long-haul over-water trips. I just don't have enough confidence in the 787 yet. I'm sure it will eventually be a fine aircraft but that's not now for me.
I'd be requesting a flight transfer if a 787 was swapped onto my existing non-787 long-haul flight at the moment.