If you are talking about the Aq. Pharm. filter, it works ok. How much water you can run through it before the cartridge needs replaced depends on your water source. In my case, I got somewhere between 25 and 40 gallons before needing to replace the filter. That translated into more expensive than buying distilled.
My RO/DI unit has made over 200 gallons and still gives a total dissolved solids reading of 0. That's a minimum of 5 replacement filters that I didn't have to buy at $15 a pop and could be as many as 8. The replacement cartridges for my RO/DI unit are $15.
The RO unit will more than pay for itself in less than 6 months.
