I've only opened up one of these kegs so far (new to homebrewing) and the tap system worked pretty well. As far as the CO2, I would not even put the cartridge in at first. When I opened mine up, I immediately charged it with some CO2 and all I was able to get out of the tap was foam. After I removed the tap and released some pressure, it worked great.
I know these systems are the subject of very mixed reviews, but I've had good results so far. I wouldn't argue that a full keg system is BETTER, but for those who can't afford kegging or don't have the space this system works pretty well.
Primary -- Boddington's Clone
Secondary -- IPA, Canadian Ale
1 Gallon Experimental Fermentor #1 -- Apfelwein
1 Gallon Experimental Fermentor #2 -- Empty
Bottled/Mini Kegs -- "We're Going Streaking" Pale Ale
, Stout, Apfelwein, Pomegranate Blueberry Apple Cider, Nut Brown Ale
Planning -- Fruit Infused Wheat Beer, Pale Ale