To start off with, I rinse and scrub all my dishes prior to putting them in the dishwasher. I hand wash pot and pans. It has been a good while since I last really looked at my dishwasher. I keep the outside and visible inside clean. My dishwasher is probably 7 years old.
Now to the ugghhhh. I decided since I found a small amount of mildew just inside the door of my dishwasher to give it a really good cleaning. I got down on my hands and knees with a flashlight and checked every crevice visible without taking it apart. It was shockingly dirty considering food never goes in it. Most of what I found was soap build up, but it is seems everywhere inside the machine. I used powdered soap for a few months twice in the last few years, never again...... The spinning arm crevices where they attach at the seams had soap build up. The door gasket, in all the moldings, inside the drainage areas all had soap build up. Looking into all the grates covering the motor area had some build up. I would have never seen all this gunk had I not been on my hands and knees with a flashlight.
This may not be a place harboring bacteria since it is just soap build up, but it cannot be helping any of us either.