As inputs I thought about the following topics:
• Current satisfaction level of the product: to measure impact of new feature (it can fill a blank or reduce latency (cf my 3rd point)
• Current usage of a feature or service: what is the impact in terms of usage: to measure adoption
• Current platform usage performance metrics: To measure impact on performance: no degradation
• If the feature objective is to improve performance or reduce latency: the gain on the metric
• The number of issues opened: This can indicate some interest, it can also help to add more doc or to identify new needs
I think this 5 points are a good start. maybe you have other ones too