Contrary to some perspectives, I did my ATP written in one day at ALL ATP's (in Mesa, AZ) and the process worked well for me (as far as simply passing the written).
I sat alone in a room with a computer, where all non-airplane (ie-LTA, Rotary wing,etc) questions had been removed from the databank, straining it down to about 685 questions. It took me about 5 hrs to go through the entire databank the first time. After a short break, it took me about 3 hrs to go through it again. I had answers (not knowledge) pouring out my ears...
Immediately, I was taken to another room where I sat at a computer to take the actual test. In little more than an hour, I was done and scored a 95.
The entire process took a little over 9 hrs.
But to be quite honest, did I really learn anything? Probably very little. And whatever that little bit was, is now buried so very deeply that I cant remember it. I was able to memorize enough information for a short time, till the test was over. But as far as learning something which impacts my day to day flying, I can not be for certain. I can only hope something useful from the experience remained.
The oral presented to me at my actual ATP check ride (NOT done at ALL ATP's) was far more demanding. It required that I be well versed in the operations, procedures, and systems of the aircraft, way beyond what was asked of me in the written. But then again, it was much more pertinent to the actual aircraft and day. But overall, very little of the information covered in the written was revisited in the oral.
So I am a success story of a "paper mill" type of operation. I successfully passed the written test, but with only a minimal amount of real learning (as far as ATP questioning goes). The process I put my own PPL and CPL students through involved much more depth and understanding of the various aspects of their respective exams, rather than just a superficial knowledge.