My story is the same as Donaldson's.
My pool came with the Frog. After I figured out what it was I bought a new mineral pac and loaded a bak pac and thought all I needed to do was adjust the little dial. It never worked well. Pool store said my levels were good but my pool water never looked crystal clear. I entered into a pattern of having the store test my water, buying what they told me to buy, and following their directions. All the while thinking this is what it took to keep a pool in shape for the summer. But after switching to the TFPC method, everything changed. Managing the pool became much easier. I knew what i was putting into the water and why. I learned the downsides and side effects of all those magic potions I had been buying for years and all that money I wasted.....
The short story is that all of these devices have the caveat that they need chlorine to cover their shortfalls. So as long as it needs chlorine, you might as well just use chlorine and save your money. It has no shortfalls when it comes to sanitation and there is a handy CYA to FC chart to ensure that your pool is always safe. All those mineral systems and ionizers are detrimental to your pool. UV can only treat the water when it passes through it. Chlorine solves the sanitation problem and is the least expensive.