Did a water change this morning, after which I made up my first batch of the Salinity salt I picked up Saturday. I didn't do any tests of the finished SW, but here's what I found:
After adding the dry salt I had a bit of a gray foam floating on the surface for a while. Most of it dissipated by the time the salt was mixed for an hour, with a bit of gray scum deposited on the outer edges of the mix bucket. I had about an inch or so of Red Sea Coral Pro mix still in the mix bucket - maybe it was a reaction between the 2 salts. I'll know better as I make additional batches of Salinity in the future.
The finished mix almost appeared to have a slight gray tinge to it. The saltwater was however nice and clear.
The salt mix at the beginning had a strange odor right after adding the dry salt. An odor unlike other salt I've used. Hard to describe it - maybe a sulfur dioxide (rotten egg) type smell? That's the only thing I can think of to describe it. The smell seemed to be gone when the mix was finished.
The salt mixed in easily for me and as quickly as any other salt I've used.
This salt is indeed much more concentrated! I added my usual amount of salt to start, after which I let it mix for 20-30 minutes, and I then measure and start making additional adds of dry salt till I get my 1.025-1.026. When I took my first test it was already at 1.026! I almost overshot the salinity, and needed no more salt adds. I can only estimate it took about 20% less salt - very nice in my opinion!
I'll add it on my next water change in about a week and hope for the best.
As a side benefit the screw on bucket lid is a nice touch to be able to easily reseal the bucket.
Edit - I just found out from gareeferman (Reggie) that the odor has been noticed by many people making up this new salt, and that SeaChem confirmed that the smell is normal due to the higher concentration of chemicals.