I think that if you're around long enough, you will probably hear everything!
Well, I'm not sure either - I was wanting to switch from IO to Reef Crystals - as I went to a reef tank- and all of my research pointed to having no issues. Some people had certain preferences, and some stated that the parameters on Ca, Alk, and Mg were all a bit different, but as long as you changed it out through normal weekly pwc's, there would be no I'll effects.
Back to the research phase!