It appears to have worked for me. I had sever grey mottling. It was classic. It started almost immediately after my pool was filled for the first time. It wasn't bad enough to re-plaster, especially after the entire pool project took 4 months (addition to the house, etc.). By the time everything was done, everybody was ready to go swimming. It seemingly got progressively worse, as described elsewhere, however, couldn't quite put a finger on it. Went through the winter, took the cover off the pool and you betcha, was willing to try anything.
Poured 6 jugs of muriatic acid and waited 2 weeks. I can't believe the results, looks beautiful. I have not been in the pool so I can't vouch for potential etching, future issues, but what choice did I have? I can always re-plaster and all things being equal, if it reduces the life of the plaster, I can live with that. My pool guys are great and will be here for me if it ever comes to that.
Just wondering. Raising the ph using baking soda is taking awhile. Is there any harm to trees, grass if I drain a bit from my acidic - now baking soda laden - pool to the surrounding area. Just trying to speed up the process.