It mixes way too high in calcium and alk for my needs - it is hard to bring back down to NSW... and y'all know how important that I think that NSW parms are for a healthy reef. It is very inconsistent - not from box to box in a batch, but from month to month. It sometimes will have dangerous levels of iodine it in and other times none. Magnesium has been over 2500 at times. I have seen fresh mixed Kent turn cuprisorb blue right after being mixed - so it had heavy metals in it... but not every time. Does anybody use it in the buckets? If so, then it is way worse since it settles more than any other salt that I have ever seen. This is the main problem with coralife - I personally believe that it is the exact same salt as the kent only it is in buckets and settles out.
I haven't used Fritz since they closed their businesses in Kansas City about twenty years ago. I don't recall much about it. If it is in a bucket, then I would suggest dry mixing it very well.
I do think that most higher-end hobbyists that are aware enough to tell subtle differences in their tanks could tell a huge difference if they switched from Kent to another salt... many, many have.
I do use the TM Pro if my calcium and alk have drifted a bit high. It mixes out around 6 and 400, so it is nearly the perfect SPS salt since a few tablespoons of baking soda will get it to 6.8.
For me, I can get IO for less a box than what the last Kent group by was, so why risk using a non-known commodity. I can probably do a group by if we can get enough for a pallet or two.