They could be, I guess. It really depends on how you're using them.
Any time you start altering you water with chemicals, you run the risk of having wild swings and fluctuations in water parameters. If you monitored everything really carefully and made sure the water was always exactly the same after a big water change, etc. then it could be fine. I always feel that stable, steady water conditions are better than playing with the chemistry of the water to create better/optimal ones. Others have probably used it with great success, though, so hopefully they will post opinions too.