What is wrong with DI water?You can use it, but in addition to the major brewing ions we are used to adjusting with salt additions, it's missing a lot of important trace elements. A little of this, a little of that, it all adds up.
Many people use RO water successfully. Once you distill or pass your water through a RO filter, any trace of those "trace" elements is effectively gone. Throw in some yeast nutrient if you're worried.
The issue with DI water (if I understand what that means) is that a de-ionizer replaces hardness with sodium ions, which affects beer flavor.