I have done the 767 on both AMS and LON to/from MSP and it is a nice enough flight. I would not fret and plan on enjoying the flight. Agree that you will actually like the middle seats for sitting together. Food is good but i would still eat a meal before getting on the plane. Well at least a large snack; i would not go on expecting to have a buffet that you will feel you didnt take advantage of.

I had the same concerns a few times myself. In the end i considered it a good use of miles.

Be sure to visit one of their clubs because you will have access on the business class leg. It makes for a more complete experience. I usually go just to stock up on newspapers & magazines and relax a bit before hand, dont expect to find much for food.