I suppose that the statisticians would consider me to be an AA failure because I dropped out soon after completing my 90 in 90. For all any AA study knows, I'm the same as someone who left and went back to the bottle. But those three months there helped get me off on the right foot and I've been sober since, for almost 4 years. The program ultimately wasn't for me because I didn't feel that I fit in for a variety of reasons - that discussion is outside the context of this thread. I do think, however, that the program ultimately helped me get on my feet again towards a successful recovery so far, and I am confident that I have taken my last drink. Couldn't imagine going back to the bottle ever again. It's infinitely easier for me to rationalize not drinking now than drinking again.
The final point is that if I had a brother who was in my shoes from four years ago, I would wholeheartedly tell him to do 90 in 90... this from an AA dropout who remains sober but would be considered an AA failure statistically.