OK, I switched from IO to Oceanic a couple of years ago, and didn't see any great change. Except that no matter whether from a bag or a bucket, the Oceanic always causes diatom blooms for several days after. A lfs owner I knew suggested I switch to Kent, and so far results are pretty nice for my softies and lps. Running low on my last bucket and haven't done a w/c in 3-4 months, and mag is down to ~1000, so picked up a small 50g jug of Oceanic. We'll see if the cursed diatoms comes back.
I'm thinking of mixing my own special blend once I see how the Oceanic turns out. What other mixes have higher ca/mag levels?