I've used IO, Reef Crystals, Tropic Marin, Oceanic, Crystal Sea, and Ocean Pure.
Currently using ocean pure (about 2 months), other than the magnesium being slightly (1150) too low, I like it.
I had been using Oceanic for almost two years and only switched to ocean pure because I got a chance to try a bunch of it at a good deal. Oceanic was zero problems and very easy for me to maintain my parameters without any supplementation. So far it is the salt I like the best.
IO, low in ca, low in mg, too high in alk. Have no plans on using it unless I have too.
Reef Crystals, Ok in ca, low in mg, too high in alk. Same as IO, I just have to supplement slightly less ca when using it. Not planning on using it again.
Tropic Marin, good ca, low in mg, high in alk. If it were not for the high alk (12dKH) I would like the salt better. For the high price it commands, I don't feel it is worth it.
Crystal sea, Never use it again, I lost a lot of corals when trying this salt as did many others. Not sure the final reason was ever found, but I do not recommend this salt at all in an SPS tank.
So my recommendations are Oceanic and Ocean Pure right now.