The visual problem in the field tiles arises partially from the irregularity of the tile edges; even if the edges are generally lined up they can still look ragged. However, you picked the tile. Nevertheless, at least some of the tiles are mis-aligned.
The niche is just plain bad! It should either have been treated as a separate area with tiles centered or as a continuation of the wall tiles. The cut in the wall tile at the top right is totally amateurish as is the switching of pattern from top to bottom. Your installer may know how to lay tile but he lacks any sense of esthetics.
Overall, I could live with the walls, not with the niche.