I use a permeate pump (water pressure powered) but on it's own it wasn't particularly good as it requires decent water pressure to operate it well and my mains pressure is quite low at about 35-40 psi. It definitely improved it but not anywhere near the claims that were made for it.
So I fitted a booster pump as well to raise the pressure to 75psi and got much better results. I use a 300gpd RO and it keeps up with me as a one man outfit. I don't know why but with the permeate pump fitted as well as the pooster pump the RO performs much better. The water goes in at around 400 ppm and comes out at between 4-6 ppm. Without the permeate pump it comes out at about between 15-20 ppm. The result is that my resin lasts much longer than before.
As an information note, the booster pump is fitted before the RO and the permeate pump is fitted after the RO but before the flow restrictor, being driven off the waste water pressure