Pros and Cons of opening wall between kitchen and dining room
Having an open layout will make the home feel larger and less constraining.
Before opening the wall:

make sure you dont have any plumbing, electrical, water in the area you want to open or else you'll have to move all of that to the side which involves lots of work.
check to make sure its not a weight bearing wall (you might have to install a header if it is).

The only con I could think of is that the 5' x 3' opening is pretty small and would make it look like a service window at the local DMV. Making the opening wider/taller would create the open space that pretty much all builders do now-a-days. If you post a picture of both side of the walls and possibly a layout, we could give our two cents.