I purchased one of these a few years back and have to say that I went back to bottling after using them for about 6 months. I probably didn't give it a proper chance, but I was always having carbonation issues using these things - sometimes overcarbonated, sometimes under. It was difficult, for me, to get the proper carbonation level I wanted..
I have also noticed that the TAD bottles (I have the blue ones.. I noticed earlier today that they recently upgraded to some amber bottles that can stand up on their own - great improvement) get damaged/scratched quite easily. Sometimes it's hard to tell if this is on the exterior of the bottle or the interior, but nonetheless I don't like storing my beers in scratched/nicked containers due to contamination concerns..
I also had problems with the bottles leaking from time to time during conditioning. I upgraded to the poly seal caps in the very beginning and still had this problem with a few bottles, BUT, like I said earlier it appears that they have improved the bottles to have flat-ish bottoms so they can stand on their own, so this shouldn't be a problem with the new system.
As mentioned above, I also tended to get very yeasty beer, but this could be avoided by using gelatin, secondary, etc etc. However, yeast does tend to get stirred up quite easily in these things as they will move some in your fridge if not properly secured. I don't know how the new bottles are in this respect, but they might have improved.
The TAD system DEFINITELY saves time on bottling day, but I felt that my beers were much better coming out of the bottle, so I switched back. With some patience, you could make this work, but IMHO I think you're best to save your money for a kegging system.
