It was really bland. I would suggest using a mixture of mushrooms. Dried mushrooms might also add some flavor. I would also suggest instead of using water just using some type of broth. I used a cup and a half of mushroom broth but really I think all the water should be substituted for broth. In all it was just really bland and I was disappointed.
By itself, this soup is really good for a healthy meal. To up the flavor, I followed the advice of another reviewer and added some dried oregano. That didn't quite cut it, so I also added about 1.5 tablespoons of Emeril's essence spice (recipe available on zaar). The final product was hearty and a bit spicy (my own doing, but I loved it!).
Thought it was very good - surprisingly hearty for a soup without a meat or chicken base. I used crushed tomatoes instead of diced. Added turmeric, dill and oregano.