I have used Instant Ocean, Reef Crystals, and Kent Reef Salt, currently using Kent Reef Salt and have had the best results, my least favorite of the three I have used was the Reef Crystals, Instant Ocean I had to dose to keep the levels where I wanted them as its pretty basic salt, but worked well for me for a long time, but the Kent Reef Salt seems to keep all my parameters right where I want them, I don't dose any more, just frequent water changes, I also only have a 40g Breeder...so...I have been happy with Kent Reef Salt.
My system is Birdsnest Dominated, but still considered mixed reef cuase I have a few LPS and softies mixed in here and there, but mostly Birdsnest, and they seem to be growing and doing great so far.