I have used Tropic Marin, Oceanic, Instant Ocean, and Red Sea before. But since trying Reef Crystals, I have had not switched. -- has given the most consistant test results over the past 6 months, so I see no reason to move off it now. However I will say that if I ever did decide to switch again, I think Red Sea would be my second choice.
The only other salt I am willing try is the Seachem stuff, but unfortunately I am unable to find it around here to test it out.