I really do not use the camera much, but yes, I have also been disappointed.
This could be due to a dirty lens (I work in a filthy environment), low light situations, or maybe the camera is just not that good.
If I was interested in taking pictures of any value, I would buy a camera, not a.phone.
I get the 'convenience' factor, but in truth their is no beating a quality product that is devoted to a single task.
Maybe if I messed with the camera more, it would interest me more. I just do not hardly use it at all. I take less than five photos a month usually, and these are usually just to show someone something and then they are deleted.
Because of security issues, I do use a non-native camera app (Simple Camera) that can sometimes cause issues on certain devices- but as far as picture quality goes, none that I am aware of.