I have used it a couple times and had no issues with my coral banded or peppermint shrimp.
In my past research I found that a lot of the cases of casualties resulting from chemiclean usage had to do with improper usage. The primary case seemed to be failing to follow the directions regarding additional oxygenation.
Adding a good sized air stone to the display and take off your skimmer cup but continue to run it overflowing back into the sump are the way to avoid this.
If you have a large cyano outbreak, I would also repeat the water change at the end, it can't hurt and if you kill a bunch cyano at the same the nutrients bound up in them must go somewhere so repeating the water change step helps remove those nutients instead of allowing some other algae to suck them up.