Every time someone says we should use Net Promoter Score I get a feeling of irritation. It is neither a metric that tells you something you can act on, nor a KPI that indicates the health of your product.
It is biased. Those who buy will be promoters, and those who don’t will be detractors.
It is lagging. In the online world you instantly see the drop in sales, engagement, or whatever core metric you are optimizing, before sending out a survey to customers asking them about the likelihood of recommending the product.
It is non-actionable. The NPS score is a result of multiple core metrics coming together. Successful companies monitor core metrics closely. If some of these metrics get better while others get messed up, it is hard to justify the change in the NPS without looking at each of the core metrics separately.
NPS – most of the time – just creates distraction. Focus on the core metrics is more actionable, and leads to better results.
If you are looking for alternatives to NPS, I think the closest metrics are retention, and virality coefficient. Those two reflect actual product usage, they are actionable, and don’t have the vanity of asking someone “Would you do this?”.