I have used it and it seems to work. However, it does have phosphates in it and will raise your phosphate level very high which can be a problem if your pool gets out of balance (phosphates can be algae food). I stopped using it and I just make sure I stay on top of my pH by not letting it get too high. If you do that, you should have no scale. Muratic acid is a lot cheaper than "The Purple Stuff". This stuff is also a metal sequesterant and there are similar products which do not use phosphonic acid. I would use that if necessary. Anyway, just a few words from my experience.

Mike