The DI essentially completes the purification through ion exchange. The concern with DI is that the resins "could" possibly leach back the salts associated with the H and OH. I suppose this could happen, but then a decent TDS meter would pick that up.
Consuming RO or RO/DI is not a bad thing. As I pointed out above, even if it did adsorb back what was removed, using K as the salt discussed, it is such a miniscule amount that it isn't worth discussing. It isn't going to weaken your bones or any other harmful effect. Any re-mineralization done is probably done on a "just in case" basis, or to quell the consumer lack of confidence based on rumors on the web. For every single article stating one thing, there is an article disputing it.
The purpose of water is to keep you hydrated and to carry the minerals you've consumed throughout your body; not supply the minerals to begin with. The human body has specific nutritional requirements, regardless of regional distribution, and assuming this diet is met for the most part, water is water is water. Reading the chemical composition of the water delivered to my house, I'll stick to the RO stuff. Not DI, because I'm cheap
