I wouldn't say it's a 50/50 split in that it works for 50% of people period, but more likely that it works for some "populations" and not others. It may be useful/effective for people with low-T, and therefore also perhaps as part of PCT (recovering test levels), but does not appear to be effective in healthy subjects with normal testosterone levels.
I'd say that it would only be potentially useful if you have low-T or perhaps as part of PCT (recovering test levels; bringing them back to baseline). As I mentioned earlier, DAA does not appear to be effective in healthy subjects with normal test levels.
Here's some new(er) research on the subject:
http://www.ncbi.nlm.nih.gov/pubmed/25844073
That's a 2 week study that found it didn't increase testosterone, and even decreased it at a higher dose.
Here's another study:
http://www.ncbi.nlm.nih.gov/pubmed/24074738
The first study I referenced regarding DAA was published recently (2015), and used subjects with at least 2 years experience resistance training, and the study also had subjects train 4-days a week. If you look at the full text (which I put a link to below), you'll see that both 3g and 6g DAA REDUCED free testosterone relative to no DAA (although the decrease was only significant in the 6g group):