The action of water conditioners does not remove the heavy metal ions, it just complexs or precipitates them, meaning that they are still present - just not available in solution at the moment.
RODI will remove such, but wastes a lot of water and removes too much IMHO, requiring the water to be reconstituted with needed materials. It is real overkill, but may well be the best in new construction situations.
I agree w/CichlidRyan - if you can't test for it, you have no idea what is happening.