A number of developers are noting that the fill rate is currently very low. Also note that they are only live in the US.
If it works correctly in test then it's probably okay. I believe the analytics available in iTunes Connect shows the number of requests as well as the number of fills and clicks.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…