Pros: Being able to look out side while doing a mundane chore. Emotional benefits! Con: ?

When possible I ALWAYS design the kitchen sink to be in front of a window. No cons.

Given a choice, I would always place the kitchen sink in front of a window.

I agree with all the previous posters. Absolutely no cons! I specifically look for this whenever I've bought a house. Even my current house, the backyard was absolutely hideous but after one year of staring at it from my kitchen sink day after day I kept getting ideas of "hmmm, maybe we should do this" and "what would look great is this..." and "honey, I think we could use a planting area there" etc. so that now, 5 years down the road the backyard is totally transformed, beautiful and I love the view out of my window! Even if the weather is miserable, I still get to spend a moment and enjoy the outdoors while doing my daily chores.

I had the choice and decided to put the sink in front of a divider and my kids lean on it and chat while I wash the dishes or pack the dishwasher. The top provides a place to stack clean dishes to be put in the china cabinet opposite. If I had put it under the window I would have had my back to everyone. A food prep bench is under the window and as I probably spend more time on food prep than dish washing it is six of one and half a dozen of the other I guess.

I am the foodie in my home and I do much of the cooking. To me, personally, I could not give a flip if there is a window in front of the kitchen or not!
BUT! I do know that a lot of people really like then. If I were building a home and it had the sink on an exterior wall I would definitely put in a window. You can always cover a window over the sink with window treatments if you do not like the view. But adding a window after the fact can be very difficult and expensive. Besides, having the window makes a kitchen feel a bit more open and airy. I would be looking for large windows in any home I was building. It will be one of the many little things that can help you get top dollar when you go to see you home later on-and nearly everyone eventually sells their home!

The point about food prep taking more time than dish washing is spot on. Thanks everyone. Since our back garden is private and lovely, doesn't seem to be any reason not to relocate the sink there.