Its been working great for me. Im at 8.2 at night and 8.3 at the peak. I use a BRS reactor and fill the cartridge to the top and that lasts me 10 days. Being that the tank is in the bottom floor of a 3-story townhouse, theres more CO2 in that room. I have noticed that when the air handler is not running (and there's been quite a bit of that happening lately since the weather has been fluctuating so much) my PH will go down to 8.15-8.25. The house is energystar certified which supposedly means airtight. I read up a bit on that certification and what I've learned is that since they make the house so airtight, they install an air exchanger to draw in outside air to minimize CO2 buildup. So my PH drop makes sense.
BTW...as mentioned above, it gets pricey. I bought the 5-gallon bucket for $100 and I dont see it lasting a year. There are tanks in this club with PH in the high 7's, low 8's and they are thriving so I plan on not ordering more once my current stock is done.