Did you know that commercial dishwasher detergent lets off low levels of chlorine fumes when mixed with water? The levels are considered "safe"- but I prefer to keep chlorine fumes out of my home as much as possible. With how much I have to run my dishwasher I will start there.
If I do buy dishwasher detergent I get one that doesn't have phosphates. My choice lately has been Seventh Generations Automatic Dishwasher Gel.
Or better yet- make your own-
Approximately 2 Tablespoons of Borax and 2 Tablespoons of Baking Soda will do a load.
We have pretty lousy water here and a not so top of the line dishwasher so I have found that the homemade solution works a lot better when I have done a good rinsing of the dishes before I put them in the dishwasher.
You can also add some vinegar to the floor of your dishwasher with any load to help reduce spots and such. You know kind of like that Jet Dry stuff.