There seems to be some misfiring because rate of likes isn't high (~1 like in 100 impressions), but based on the people that like the promoted post it is 100% without exception accurate. So, at the least, it is reaching the right people. I know because there are currently 500+ likes and I've visited every single profile and tried to engage with them. Audience is just developers.

I must say, it has been a very positive ad experience – receive compliments, 10% retweets, and had several long form conversations with strangers on Twitter messages. Really fun.