Originally Posted by dobeluvr
Don't know about taste, but it will allow a person to carbonate more kegs than they have room for on tap.
I find it helps the seal also. I've pressurized to 30 lbs without sugar, and went back the next day to find barely any pressure at all, making me wonder what would it have done if I hadn't checked it for a few days. Leak? I doubt it, as it is fine if I add the sugar and leave it for weeks.
When you pressurize it to 30 lbs and leave it you only pressurize the head space, and then the beer absorbs the CO2, making it carbonated, the head space now has less pressure because the beer has absorbed most of the CO2 when reaching equilibrium.
When you add sugar and leave it for weeks the yeast eats the sugar and constantly produces CO2 until all of the sugar is gone. This carbonates the beer and adds pressure.
If you want to pressureize and carbonate without priming sugar you either have to leave it connected to the CO2 bottle, or charge the keg up with the CO2 bottle every so often to repressurize the head space so more CO2 can be absorbed into the beer, (just make sure not to over carbonate that way)