I use Reef Crystals. It's not in the poll, but it is made by Instant Ocean, so maybe I should vote Instant Ocean?
Anyhow, main reason I started to use it is because the LFS carries it, both IO regular and IO RC. Cheap, no delivery charges. Now, I order it online because I order the box good for 200 gallons, free delivery and cheaper than the LFS. I still use it because it has higher alk, calcium and mag numbers. Cut's down on my dosing needs.